Mixed-gas species plasma source system

Abstract

To provide an ion beam system optimizing a mixture of multiple unique gas species in a plasma source.SOLUTION: An ion beam system includes a plasma source tube defining a plasma source chamber, a first gas reservoir housing a first gas, a second gas reservoir housing a second gas, a first controller fluidly coupled to the first gas reservoir and configured to control a first flow rate of the first gas, and a second controller fluidly coupled to the second gas reservoir and configured to control a second flow rate of the second gas. The system also includes a first capillary constriction including a first end fluidly coupled to the first controller and a second end fluidly coupled to the plasma source chamber, and a second capillary constriction including a third end fluidly coupled to the second controller and a fourth end fluidly coupled to the plasma source chamber, where the first capillary constriction and the second capillary constriction are distinct.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to a mixed gas species plasma source system.

Background Art

[0002] Charged particle beam systems are used in a variety of applications including the manufacture, repair, and inspection of small devices such as integrated circuits, magnetic recording heads, and photolithography masks. In certain types of charged particle beam systems, ions are generated by ionizing a gas within a plasma source. These ions are then directed at a sample in a beam in order to perform processing or imaging steps, as well as to physically alter the sample. The ion species utilized for this purpose can be tailored to a particular sample or process by changing the gas species that is ionized within the plasma source. A particular sample or process may require a mixture of multiple unique ion species and thus a mixture of multiple unique gas species within the plasma source. There is a need for a new charged particle beam system that optimizes this gas mixing.

Summary of the Invention

[0003] One aspect of the present disclosure provides an ion beam system. The ion beam system also includes a plasma source tube that defines a plasma source chamber. The system also includes a first gas reservoir that stores a first gas and a second gas reservoir that stores a second gas. The system also includes a first controller fluidly coupled to the first gas reservoir and configured to control a first flow rate of the first gas, and a second controller fluidly coupled to the second gas reservoir and configured to control a second flow rate of the second gas. The system also includes a first capillary constriction including a first end fluidly coupled to the first controller and a second end fluidly coupled to the plasma source chamber, and a second capillary constriction including a third end fluidly coupled to the second controller and a fourth end fluidly coupled to the plasma source chamber, wherein the first capillary constriction and the second capillary constriction are separate.

[0004] Another aspect of the present disclosure provides an ion beam system. The ion beam system also includes a plasma source tube that defines a plasma source chamber. The system also includes a first gas reservoir that stores a first gas species and a second gas reservoir that stores a second gas species. The system also includes a first controller fluidly coupled to the first gas reservoir and configured to control a first flow rate of the first gas species. The system also includes a first capillary constriction including a first end fluidly coupled to the first controller and a second end fluidly coupled to the plasma source chamber. The system also includes a computer system configured to communicate with the first controller and provide instructions to operate the first controller.

[0005] Yet another aspect of the present disclosure provides a non-transitory computer-readable storage medium storing computer-readable instructions of a program. The non-transitory computer-readable storage medium also includes instructions for causing a first controller to open a first variable outlet pressure valve and discharge a first gas at a first flow rate from a first gas reservoir through a first capillary constriction into a plasma source chamber defined in a plasma source tube. The medium also includes instructions for causing a second controller to open a second variable outlet pressure valve and discharge a second gas at a second flow rate from a second gas reservoir through a second capillary constriction into the plasma source chamber such that the first and second gases are mixed within the plasma source chamber, the second capillary constriction being separate from the first capillary constriction.

Brief Description of the Drawings

[0006] A further understanding of the nature and advantages of various embodiments can be realized by referring to the following figures. In the accompanying drawings, like components or features can have the same reference label. Further, various components of the same type can be distinguished by following the reference label with a dash and a second label that distinguishes between like components. If only the first reference label is used herein, the description is applicable to any one of the like components having the same first reference label regardless of the second reference label.

Figure 1

Figure 2A

Figure 2B

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Figure 8

DETAILED DESCRIPTION

[0007] An ion beam system is a type of charged particle beam system used to modify a sample (e.g., by milling). In particular, a focused ion beam (FIB) performs milling by physically removing atoms and molecules from the surface of a sample via a process known as physical sputtering. FIB systems generally operate by directing a focused beam of ions onto the surface of a sample, such as a raster pattern. In one example, these ions can be extracted from a plasma source and accelerated and focused onto the sample using a series of apertures and electrostatic lenses. Specifically, these plasma sources ionize a gas or a mixture of gases within a plasma source chamber and extract the ions to form a beam that is focused onto the sample. The particular material of the sample, or the process being performed on that material, may require a mixture of process gases in a specific ratio to generate a mixed-species ion beam that optimally mills the sample. Providing a specific ratio of gas species in the gas mixture for each particular sample can be difficult.

[0008] One way to supply a gas mixture involves supplying a pre-mixed gas mixture to a plasma source. This can be achievable if the pre-mixed gas mixture contains the exact ratio of gases that are used to extract an optimal ion beam for milling a sample (e.g., milling a non-uniform or various types of material layers), but problems can arise if the pre-mixed gas mixture does not contain this specific ratio of gases. Specifically, since the gas mixture is pre-mixed, the ratio of gases in the gas mixture cannot be changed dynamically (e.g., the ratio of gases in the gas mixture cannot be changed while the sample is being milled). Thus, using a pre-mixed gas mixture results in reduced flexibility.

[0009] Another way to provide a gas mixture may include mixing the gases at a high-pressure gas inlet (e.g., above 1 bar) just outside the plasma chamber and introducing the gas mixture into the plasma source chamber using a constriction. However, if the mixing is done at high pressure before the constriction, it can be difficult to control and adjust the desired partial pressures of each gas within the plasma cell. Furthermore, the constriction region (e.g., from precisely crimping a tube) can vary between each system due to manufacturing variability, which can result in a constriction with an irregular cross-sectional shape and make it difficult to consistently control the pressure using this method. The leak rate discrepancies can be seen either between different units or over time within the same unit. Additionally, since the high-pressure gas must be removed from the entire gas supply line to provide a new gas mixture, changing the gas mixture can take a long time (e.g., about 10 minutes) and can lead to unnecessary waste of expensive gases. Thus, using this large pressure drop at the constriction can be difficult, inconsistent, and expensive.

[0010] The present disclosure provides a plasma source system that includes a controller capable of selectively and individually controlling the supply of each specific gas species. In particular, each controller controls the pressure or differential flow rate of each gas species mixed into the gas mixture so as to more dynamically and accurately control the composition of the gas mixture and be able to accommodate different sample materials. The present disclosure also includes a capillary constriction fluidically separated from the gas supply line such that gas within the capillary constriction can be evacuated without the need to evacuate the gas supply line. Thereby, waste of gas can be minimized and costs can be saved. The capillary constriction may also be smaller than a conventional gas supply line in order to further minimize gas waste and save costs by evacuating even less gas than a conventional plasma source system.

[0011] The remainder of the description makes daily reference to an FIB system, but it will be readily understood by those skilled in the art that the technology is not so limited. The present design can be used with other types of charged particle microscopes including a scanning electron microscope (SEM), a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), a dual beam system including an ion beam source and an electron beam source, a reflection electron microscope (REM), a circuit editing microscope, and the like. Accordingly, the present disclosure and the claims should not be regarded as limited to any particular exemplary microscope discussed, but can be widely utilized with any number of charged particle microscopes that may exhibit some or all of the electrical or chemical characteristics of the examples discussed.

[0012] FIG. 1 shows an exemplary charged particle system 100 (e.g., an FIB system). For the sake of brevity, additional details regarding charged particle systems such as the focusing column and the sample chamber are not shown. Gas is supplied from an external gas supply line 104 through a gas filter 106 to a plasma source chamber 102 within a plasma source tube 103 and then to a tube 108 having a constriction 110. Energy is supplied from a radio frequency (RF) power source 113 by an antenna coil 114 to the plasma source chamber 102, and ions are extracted through a source electrode opening 116 within a source electrode 118 by an extraction electrode 120.

[0013] A plurality of gas sources, such as a first gas reservoir 130a, a second gas reservoir 130b, a third gas reservoir 130c, and a fourth gas reservoir 130d, supply gas to a gas supply line 104 via respective valves 131a, 131b, 131c, 131d (e.g., pressure regulators, bypass valves, etc.). Each of the gas reservoirs 130a, 130b, 130c, 130d may contain a gas species for generating plasma (e.g., oxygen, xenon, krypton, argon, nitrogen, hydrogen, etc.). The gas flows downstream from the gas reservoirs 130a, 130b, 130c, 130d to the plasma source chamber 102 through a constriction 110 of a tube 108 and exits through an opening 116 of a source electrode 118. A pump 122 can be connected to the gas supply line 104 via a valve 123 and can be operated to remove gas from the plasma source chamber 102 via the tube 108 and the gas supply line 104. An ion column pump (not shown) extracts gas from the plasma source chamber 102 through a source electrode opening 116. A beam voltage source 132 supplies a high voltage to the plasma in the chamber 102, and an extraction voltage source 134 supplies a voltage to an extraction electrode 120. The extracted ions or electrons are focused towards a sample chamber (not shown) containing a sample using a focusing electrode 136. To remove gas from the interior of the plasma source chamber 102, the valve 123 can be actuated to pump out gas upstream from the gas supply line 104 and the plasma source tube 103 and downstream from the source electrode opening 116 from a main chamber vacuum pump(s) (not shown).

[0014] The tube 108 can facilitate calibrated leakage from the gas supply line 104 to the plasma source chamber 102. Specifically, the portion of the plasma source system 100 upstream of the tube 108 can be pressurized to be larger than the portion of the plasma source system 100 downstream of the tube 108 (e.g., within the plasma source chamber 102) such that gas flows downstream from the gas supply line 104 to the plasma source chamber 102. Further, the tube 108 can define a constriction 110 to have a specific diameter (e.g., less than about 1 mm such as about 5 - 10 microns) so that gas flows into the plasma source chamber 102 at a desired pace.

[0015] As described above, because various gas flows are mixed within the large gas supply line 104 before reaching the tube 108, it can be difficult to accurately control the partial pressure, and thus the flow rate, of each gas species in the gas mixture immediately upstream of the tube 108. Additionally, since the constriction 110 requires a very precise diameter to ensure that gas enters the plasma source chamber 102 at an accurate flow rate, the diameter can vary among manufacturers and may not be consistent. Therefore, it becomes even more difficult to control the pressure of the gas entering the plasma source chamber 102. Finally, when changing the gas mixture, the entire gas supply line 104 (e.g., the gas within the gas supply line 104 from between the valves 123, 131a, 131b, 131c, 131d to the tube 108) must be purged, leading to gas waste and requiring long purge times.

[0016] These problems are addressed by the described plasma source system having individual controllers, along with different ways of introducing a gas mixture into the plasma source chamber of the plasma source system and discharging the gas mixture from the plasma source chamber. For example, FIGS. 2A and 2B show an exemplary charged particle system 200 that includes a plasma source system 280 and a computer system 290 (similar to the computer system 810 shown in FIG. 8) that communicates with the plasma source system 280 to provide instructions for operating the plasma source system 280. As noted above, additional details regarding the charged particle system 200, such as the focusing column and the sample chamber, are not shown. Features that end with reference numbers similar to those of the features discussed above are understood to be similar, except as otherwise described below.

[0017] The plasma source system 280 includes a first gas reservoir 230a and a second gas reservoir 230b that are fluidly coupled to the chamber body 260 via respective gas valves 231a, 231b (e.g., pressure regulators, bypass valves, etc.), gas supply lines 204a, 204b, and controllers 240a, 240b. The chamber body 260 defines a first capillary constriction 250a, a second capillary constriction 250b, a bypass manifold 252 that defines a bypass chamber 254, a plasma source tube 203 that defines a plasma source chamber 202, and an internal volume 262 that houses an antenna coil 214. Each of the gas reservoirs 230a, 230b may include a corresponding gas supply line, a pump valve 223a, 223b, a pump 222a, 222b, a gas valve 231a, 231b, a controller 240a, 240b, and a capillary constriction 250a, 250b. Although only two gas reservoirs 230a, 230b are shown, in other embodiments, there may be any number of gas reservoirs, such as one, three, four, five, etc. In these examples, each of the gas reservoirs may include a corresponding gas supply line, a pump, a gas valve, a controller, and a capillary constriction. Each of the respective gas reservoirs 230a, 230b, gas supply lines 204a, 204b, pump valves 223a, 223b, pumps 222a, 222b, controllers 240a, 240b, and capillary constrictions 250a, 250b may be fluidly coupled to each other such that gas can flow from the gas reservoirs 230a, 230b through the gas supply lines 204a, 204b, controllers 240a, 240b, and capillary constrictions 250a, 250b and be mixed within the plasma source chamber 202.

[0018] FIG. 2A shows the gas flowing downstream into the plasma source chamber 202 from the gas reservoirs 230a, 230b through the gas supply lines 204a, 204b, the controllers 240a, 240b, the capillary constrictions 250a, 250b, and the bypass chamber 254 to generate the plasma 255. The ion species ratio of the ion beam extracted from the plasma 255 can be measured by measurement units 275 (e.g., residual gas analyzer, mass spectrometer, etc.) disposed on the sample, within the ion beam column, and the like. FIG. 2B shows the discharge of the gas used to generate the plasma 255 by instructing the bypass actuator 242 to move the bypass manifold 252, as will be further described below. As described above, in other examples of plasma sources, it is difficult, inconsistent, and potentially wasteful to control the pressure and gas flow rate for a more accurate gas mixture composition. The capillary constrictions 250a, 250b and the controllers 240a, 240b address these issues.

[0019] Controllers 240a and 240b can be fluidly coupled between gas supply lines 204a and 204b and capillary constrictions 250a and 250b such that the controllers 240a and 240b control the flow rate of gas entering capillary constrictions 250a and 250b from gas supply lines 204a and 204b. Thereby, the flow rate of gas entering bypass chamber 254 and then plasma source chamber 202 can be controlled. For example, controllers 240a and 240b can include variable outlet pressure valves that control the pressure from gas supply lines 204a and 204b to capillary constrictions 250a and 250b and can provide a variable flow rate. In this way, controllers 240a and 240b can adjust the partial pressure of each gas species in the gas mixture used to generate plasma 255 to adjust the composition of the gas mixture. Controllers 240a and 240b enable the gas mixture to be dynamically adjusted (e.g., adjusted in real time while ions are being extracted) without requiring the discharge of the gas mixture. Controllers 240a and 240b can also include pressure sensors for detecting the gas pressure in gas supply lines 204a and 204b and / or capillary constrictions 250a and 250b. Controllers 240a and 240b can be instructed to release gas into capillary constrictions 250a and 250b at least partially due to the pressure measurements detected by the pressure sensors.

[0020] In some embodiments, controllers 240a, 240b can control the pressures both upstream and downstream of controllers 240a, 240b. For example, controllers 240a, 240b can control the pressure downstream of controllers 240a, 240b by controlling a relief valve to allow gas to flow from gas supply lines 204a, 204b into capillary constrictions 250a, 250b. Controllers 240a, 240b can control the pressure upstream of controllers 240a, 240b by controlling relief port valves 244a, 244b included in controllers 240a, 240b. Relief port valves 244a, 244b may be in fluid communication with a vacuum source (e.g., internal volume 262, as described below) to allow gas from gas supply lines 204a, 204b and capillary constrictions 250a, 250b to flow through relief port valves 244a, 244b toward the vacuum source. For example, relief port valves 244a, 244b can allow gas in gas supply lines 204a, 204b to flow downstream through relief port valves 244a, 244b and be discharged to the vacuum source, while gas in capillary constrictions 250a, 250b can flow upstream through capillary constrictions 250a, 250b and be discharged to the vacuum source through relief port valves 244a, 244b.

[0021] Controllers 240a and 240b can control relief port valves 244a and 244b such that the controllers 240a and 240b can discharge the gas in gas supply lines 204a and 204b. In this way, the gas in gas supply lines 204a and 204b can be discharged at one end by controllers 240a and 240b and at the other end by pumps 222a and 222b, thereby facilitating the gas discharge of gas supply lines 204a and 204b. Additionally or alternatively, controllers 240a and 240b can control the opening of relief port valves 244a and 244b to discharge the gas in capillary constrictions 250a and 250b. In this way, the gas in capillary constrictions 250a and 250b can be discharged in both the downstream and upstream directions, further facilitating the gas discharge of capillary constrictions 250a and 250b without the need to discharge the gas in gas supply lines 204a and 204b, as will be further described below. Controllers 240a and 240b can also control relief port valves 244a and 244b to discharge gas simultaneously from both supply lines 204a and 204b and capillary constrictions 250a and 250b, thereby facilitating the discharge of all the gas from plasma source system 280.

[0022] Controllers 240a and 240b are fluidly coupled to capillary constrictions 250a and 250b to more accurately control the partial pressure of each gas from gas reservoirs 230a and 230b in order to individually control the flow rate of each gas species entering the gas mixture. Additionally, capillary constrictions 250a and 250b can differ from each other to facilitate this increased accuracy by ensuring that each gas is delivered directly into bypass chamber 254 at a specific pressure without being altered by the introduction of other gases. Capillary constrictions 250a and 250b can differ from each other if the gases within each of capillary constrictions 250a and 250b do not interact with other gases until they are mixed within plasma source chamber 202. For example, capillary constrictions 250a and 250b may be spaced apart from each other. Capillary constrictions 250a and 250b may also not cross each other. Capillary constrictions 250a and 250b may also be separated from each other. In this way, controllers 240a and 240b can be individually adjusted to allow a specific gas flow rate of each gas to enter bypass manifold 252, thus allowing for more accurate control of the pressure of each gas at the total pressure of the gas mixture.

[0023] Furthermore, since each of the capillary constrictions 250a, 250b is different from each other, each of the controllers 240a, 240b can sense the pressure of each gas species in the corresponding gas supply lines 204a, 204b without potentially interfering with the pressure sensors in each of the controllers 240a, 240b due to the pressure of other gas species. In this way, the controllers 240a, 240b can more accurately sense the pressure of each gas species in the gas supply lines 204a, 204b. Next, these more accurate pressure measurements can enable the controllers 240a, 240b to more accurately and precisely control the flow rate of the gas entering the capillary constrictions 250a, 250b. This can be particularly beneficial compared to other embodiments where the pressure of other gases can interfere with the pressure sensing of the controller (e.g., when the controller is arranged along the same gas supply line as the valves 131a, 131b, 131c, 131d shown in FIG. 1). In such an embodiment, the pressures from each of the gases in the supply line are mixed together such that the controller cannot sense the partial pressure of each gas species. This embodiment cannot accurately control the partial pressure of each gas species in the gas mixture and thus cannot accurately control the composition of the gas mixture. This problem can be exacerbated in embodiments using constrictions because the volume of the gas supply line between the controller and the constriction may make it less likely that the actual pressure of each gas downstream of the volume represents the sensed pressure of each gas upstream of the volume (e.g., where the controller is located), adding difficulty in controlling the gas mixture composition.

[0024] On the one hand, before the gas is mixed in the plasma source chamber 202, the controllers 240a, 240b directly connected to the corresponding capillary constrictions 250a, 250b can more accurately control the composition of the gas mixture. This can be beneficial for optimizing the milling and polishing operations by making small adjustments to the gas mixture composition specific to each layer of the sample material. This can also enable the milling process for a particular material to be accelerated or decelerated as desired. Further, this dynamic adjustment of the gas mixture can minimize the gas shadowing effect by controlling the volatilization and redeposition of the sputtered material.

[0025] The controllers 240a, 240b can individually release gas independently of each other. For example, even in a situation where the gas supply lines 204a, 204b contain the same pressure, the first controller 240a can release gas from the downstream first gas supply line 204a to the first capillary constriction 250a at a first flow rate different from the second flow rate at which the second controller 240b releases gas from the second gas supply line 204b to the second capillary constriction 250b. In this way, the gas from the gas reservoirs 230a, 230b can be released into the bypass chamber 254 simultaneously or periodically.

[0026] The controllers 240a, 240b can release gas simultaneously by releasing gas into the corresponding capillary constrictions 250a, 250b at a flow rate greater than zero. This can include releasing gas from each of the gas supply lines 204a, 204b into the capillary constrictions 250a, 250b at the same flow rate or different flow rates. The controllers 240a, 240b can release gas at a constant flow rate so that the composition of the gas mixture is kept constant for a period (e.g., when milling a layer of the sample material). The controllers 240a, 240b can additionally or alternatively release gas at a variable rate so that the composition of the gas mixture changes over a period (e.g., when milling through a transition in the sample material).

[0027] During the first period, controllers 240a and 240b can periodically release gas by setting the first flow rate of the first gas to zero (e.g., stopping the downstream flow of the gas) and setting the second flow rate of the second gas to non - zero. After the first period, controllers 240a and 240b can then set the first flow rate to non - zero and set the second flow rate to zero during the second period. Thus, controllers 240a and 240b can periodically release gas by circulating at least one downstream gas flow rate to zero in this way. In some embodiments, when there are three or more gas reservoirs, the controller may release some of the gases in tandem while circulating other gases. For example, the controller can release two or more gases at the same or different non - zero flow rates while setting one or more of the other gases to a zero flow rate for a period of time and circulating at least one gas to have a zero flow rate over each period.

[0028] Controllers 240a, 240b and capillary constrictions 250a, 250b may be fluidly coupled, while at least one of controllers 240a, 240b and capillary constrictions 250a, 250b is directly coupled to the chamber body 260. The chamber body 260 can define an opening adjacent to controllers 240a, 240b such that capillary constrictions 250a, 250b can be fluidly coupled to controllers 240a, 240b without being directly coupled to each other. For example, a portion of controllers 240a, 240b can extend through the chamber body 260 to fluidly couple capillary constrictions 250a, 250b to controllers 240a, 240b. In another example, capillary constrictions 250a, 250b can extend through the chamber body 260 to fluidly couple capillary constrictions 250a, 250b to controllers 240a, 240b. In yet another different example, capillary constrictions 250a, 250b and controllers 240a, 240b may be coupled to both sides of the chamber body 260, but may also be fluidly coupled to each other through the opening of the chamber body 260.

[0029] The controllers 240a and 240b can discharge gas from the gas supply lines 204a and 204b into the capillary constrictions 250a and 250b at any flow rate between the maximum flow rate at which gas is discharged into the capillary constrictions 250a and 250b at a pressure equal to the pressure in the gas supply lines 204a and 204b and the minimum flow rate at which no gas is discharged into the capillary constrictions 250a and 250b. In this way, the controllers 240a and 240b can act as a stop in the gas flow path between the gas supply lines 204a and 204b and the capillary constrictions 250a and 250b so that the gas in the gas supply lines 204a and 204b is fluidly isolated from the capillary constrictions 250a and 250b. Thereby, the pressure in the gas supply lines 204a and 204b can be maintained at a constant pressure, and the pressure in the capillary constrictions 250a and 250b can be made variable. As will be further described below, this can be beneficial when discharging the gas mixture because only the gas in the capillary constrictions 250a and 250b, rather than the entire gas supply lines 204a and 204b (like the gas supply line 104 in FIG. 1), needs to be discharged.

[0030] The capillary constrictions 250a, 250b may each be a tube having respective first ends 251a, 251b coupled to the chamber body 260 and respective second ends 253a, 253b coupled to the bypass manifold 252. The diameters of the capillary constrictions 250a, 250b may be sized to improve their high voltage standoff, and thus minimize any plasma creep within the capillary constrictions 250a, 250b and minimize arc discharge. For example, the diameter may be sized to reduce the mean free path length of the gas within the plasma cell. This can help prevent high voltage dielectric breakdown by gradually reducing the pressure across the capillary constriction to a level that withstands Paschen dielectric breakdown due to the high electric field potential within the plasma region. The capillary constrictions 250a, 250b may be made of an electrical insulating material (e.g., plastic, rubber, etc.) to further protect from arc discharge. The inner surfaces of the capillary constrictions 250a, 250b defining the inner diameter may also include a fused silica lining to resist carbonization due to arc generation and resist gas release. The length may be sized to provide sufficient flow rate to maintain the plasma cell pressure and allow for tunability of the gas mixture.

[0031] For example, the capillary constrictions 250a, 250b may have a diameter of about 100 μm, such as less than about 75 μm, less than about 50 μm, or less than about 25 μm. Since this diameter can be more consistent than the constrictions defined in the tubes of other plasma source systems, the delivery of gas through the capillary constrictions 250a, 250b can be more consistent and repeatable. The capillary constrictions 250a, 250b may have a length of about 50 to 280 mm, such as about 75 mm to 175 mm, or for example about 100 to 150 mm. This length can allow components sensitive to the plasma arc (e.g., controllers 240a, 240b, the ground enclosure, or other structural components) to be positioned far enough away from the region of high electric field potential to prevent arcing due to proximity. In a preferred embodiment, the capillary constrictions 250a, 250b may have a preferred diameter of about 50 μm and a length of about 150 mm. The capillary constrictions 250a, 250b may have similar dimensions, but in other embodiments, each of the capillary constrictions may have different dimensions. In a further alternative, if there are more than three capillary constrictions, only some of the capillary constrictions may have similar dimensions (e.g., two of the three capillary constrictions have similar dimensions). These dimensions can minimize the pressure drop across the capillary constrictions 250a, 250b (e.g., about 100 to 1000 millibars) compared to the larger pressure drops (e.g., about 2 to 3 bar) when using constrictions within other plasma source systems, and thus allow for easier control of the pressure and flow rate of the gas entering the capillary constrictions 250a, 250b compared to the gas entering the constrictions within those other systems.

[0032] As will be further described below, due to the small sizes of the capillary constrictions 250a and 250b and thus the small volumes of gas that each capillary constriction 250 can hold, waste of gas when discharging gas from the plasma source system 280 can be reduced. Further, the capillary constrictions 250a and 250b can have a less complex shape (e.g., like the constriction 110 in FIG. 1, without including a change in diameter along its length), and a less expensive material can be used (e.g., using a plastic material instead of a metal), so the capillary constrictions 250a and 250b can be less expensive than other components used for delivering gas, such as the tube 108 in FIG. 1. However, in other embodiments, the capillary constriction may have a non-uniform diameter along its length and any type of material including glass (e.g., silica), metal, etc. may be used.

[0033] The chamber body 260 may be in fluid communication with a vacuum source (e.g., vacuum pump 270) such that the internal volume 262 is under vacuum. However, in other embodiments, the internal volume 262 may not be in fluid communication with the vacuum source. Instead, the vacuum source may be in fluid communication with other components of the charged particle system, such as a bypass chamber and / or a controller. In this way, as further described below, gas can be exhausted through the bypass chamber and / or the controller. The bypass manifold 252 may be structured to define a bypass chamber 254 such that when the bypass manifold 252 and the plasma source tube 203 are coupled to each other, the bypass manifold 252 can fluidly isolate the capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 from the internal volume 262, as shown in FIG. 2A. In this way, the gas in the capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 can be used to generate plasma 255 without escaping into the internal volume 262. In some embodiments, a controller can be fluidly coupled between the bypass chamber and the plasma source chamber. This can be beneficial for controlling the gas flow into the plasma source until desired. For example, the controller can stop the gas from entering the plasma source until all the gas is properly mixed within the bypass chamber to form a homogeneous gas mixture. Once the gas mixture is formed, the controller can release the gas mixture from the bypass chamber into the plasma source chamber.

[0034] As described above, other plasma source systems typically require the entire system gas to be completely evacuated when switching the gas species used in the gas mixture (e.g., pump 122 evacuates gas from all of the plasma source chamber 102, tube 108, and gas supply line 104 of FIG. 1). This is costly because wasting such gas is expensive. Further, it takes an unnecessarily long time to evacuate the entire system. The plasma source system of the present disclosure addresses these problems by enabling the gas species to be changed by partially evacuating the system, resulting in significantly less gas waste.

[0035] The gas from the plasma source system 280 can be partially evacuated by evacuating only the gas in the plasma source chamber 202, bypass chamber 254, and capillary constrictions 250a, 250b. Specifically, the bypass actuator 242 can be commanded to move the bypass manifold 252 from the first state shown in FIG. 2A to the second state shown in FIG. 2B by moving the bypass manifold 252 away from the plasma source tube 203. This allows the gas in the capillary constrictions 250a, 250b, bypass chamber 254, and plasma source chamber 202 to escape into the internal volume 262 along arrow A. The gas can then be evacuated from the charged particle system 200 by flowing to a vacuum source. The distance that the bypass manifold 252 moves from the first state to the second state is for illustrative purposes only, and it should be understood that the bypass manifold 252 can move any distance between states to enable gas evacuation. In other embodiments, if the bypass chamber and / or controller is in fluid communication with the vacuum source instead of the internal volume, the gas can be evacuated to the vacuum source through the bypass chamber and / or controller.

[0036] Since the gas from the gas supply lines 204a and 204b does not need to be discharged during this gas species change, the gas in the gas supply lines 204a and 204b is not wasted unnecessarily. Further, this partial discharge saves time by eliminating the need to discharge the gas supply lines 204a and 204b to change the gas species. Additionally, the capillary constrictions 250a and 250b can be made significantly smaller (e.g., about 50,000 to 200,000 times smaller) than the gas supply lines used in other plasma source systems (e.g., the gas supply line 104 in FIG. 1), thus requiring even less gas to be discharged, and therefore saving even more time and further minimizing gas waste.

[0037] In addition, changing the gas species can be overall faster, as shown in the example where there are three or more gas reservoirs and one or more gas species are exchanged. In this example, the gas valve can release three or more gas reservoirs and pressurize their respective gas supply lines, but only the first controller releases the first gas species of the first gas reservoir to the first capillary constriction, and the second controller releases the second gas species of the second gas reservoir to the second capillary constriction to form a first gas mixture. After the process, it may be desirable to exchange the first gas species with a third gas species that has not yet been introduced into the plasma source chamber but has already been released into the corresponding gas supply line. The first and second gas species can be discharged from their respective capillary constrictions without discharging the gas supply lines of all the gas reservoirs, as described above. Then, the second controller can release the second gas species and return it to the second capillary constriction, while the third controller can release the third gas species to the third capillary constriction to form a second gas mixture that does not contain the first gas species. This process emphasizes further advantages of the capillary constrictions and the controllers, as the discharge of the first and second gas species is faster and less wasteful, as well as the introduction of the third gas species is faster, as described above. Specifically, the third gas supply line corresponding to the third gas reservoir is already pressurized and ready to be introduced into the third capillary constriction (and thus into the bypass chamber and the plasma source chamber), so the time required to form this second gas mixture is shorter compared to other plasma source systems that require discharging and repressurizing the entire gas supply when changing the gas species.

[0038] By using the relief port valves 244a, 244b defined within the controllers 240a, 240b, the gas within the capillary constrictions 250a, 250b can be more favorably discharged without wasting the gas within the gas supply lines 204a, 204b. Specifically, the controllers 240a, 240b can control the relief port valves 244a, 244b such that the gas within the capillary constrictions 250a, 250b is discharged from the first ends 251a, 251b simultaneously with the gas being discharged from the second ends 253a, 253b through the bypass chamber 254 into the internal volume 262. Since the controllers 240a, 240b can control the relief port valves 244a, 244b to enable the discharge of the gas within the capillary constrictions 250a, 250b without affecting the gas within the gas supply lines 204a, 204b, the gas within the gas supply lines 204a, 204b is not wasted by using the relief port valves 244a, 244b to discharge the gas within the capillary constrictions 250a, 250b.

[0039] When the entire plasma source system 280 (e.g., all gas supply lines 204a, 204b, capillary constrictions 250a, 250b, bypass chamber 254, and plasma source chamber 202) is being evacuated, the charged particle system 200 can evacuate the gas faster than other plasma source systems. By using the relief port valves 244a, 244b, the gas within the gas supply lines 204a, 204b can be evacuated from both ends, i.e., from one end by the pumps 222a, 222b and from the other end by the corresponding relief port valves 244a, 244b within the controllers 240a, 240b. In this way, the gas supply lines 204a, 204b can be more favorably evacuated compared to other plasma source systems that evacuate the gas supply lines using only a pump (e.g., pump 122 of FIG. 1). In some embodiments, the gas within the gas supply lines can be evacuated without evacuating the gas within the capillary constrictions, bypass chamber, and plasma source chamber.

[0040] FIG. 3 shows a diagram 300 depicting the gas flow paths of the plasma source system. Features ending with reference numerals similar to those discussed above are understood to be similar, except as described below. As shown, the plasma source can have any number of gas reservoirs 330a, 330b, 330c, 330...n. The following description focuses on the gas flow path of the first gas from the first gas reservoir 330a, but it is understood that the gas flow paths of the other gases from the other gas reservoirs 330b, 330c, 330...n can follow corresponding similar paths as shown in FIG. 3.

[0041] When introducing gas into the plasma source chamber 302, the first gas from the first gas reservoir 330a can be released (e.g., via a gas valve such as valve 231a in FIGS. 2A and 2B) to enter the corresponding gas supply line (e.g., gas supply line 204a). The first gas can flow along the gas supply line along the first flow path A1 to both the first controller 340a and the first pump 322a. At this point, the first pump 322a may not be activated, and thus the first gas may not be released to a vacuum source. The first controller 340a can be opened to release the first gas into the capillary constriction 350a leading to the bypass chamber 354 via the second gas flow path B1. Then, this first gas flows from the bypass chamber 354 into the plasma source chamber 302 along the third gas flow path C and can be mixed with one or more other gases (if present) from the other gas reservoirs 330b, 330c, 330...n to form a gas mixture. This gas mixture can then be used for plasma generation and ion beam extraction.

[0042] When only the gas in the capillary constriction 350a, the bypass chamber 354, and the plasma source chamber 302 is exhausted, the bypass actuator (e.g., bypass actuator 242) may be commanded to move the bypass manifold (e.g., bypass manifold 252) away from the plasma source tube (e.g., plasma source tube 203) such that the gas in the capillary constriction 350a, the bypass chamber 354, and the plasma source chamber 302 flows into the internal volume 362 along the fourth flow path D. These gases can then flow towards the vacuum source along the fifth flow path E. These gases can also be exhausted from the other end of the capillary constriction 350a when the controller 340a opens the relief port valve (e.g., relief port valve 244a in FIGS. 2A and 2B) and exhausts the gas through the capillary constriction 350a along the sixth flow path F1. When exhausting the gas from the gas supply line, the pump 322a can exhaust one end of the gas supply line such that the gas flows from the gas supply line along H1 towards the vacuum source. The controller 340a can open the relief port valve to exhaust the gas from the other end of the gas supply line such that the gas flows from the gas supply line along G1 towards the vacuum source.

[0043] Figures 4, 5, 6, and 7 show exemplary flow diagrams illustrating respective processes 400, 500, 600, and 700, as described herein. Processes 400, 500, 600, and 700 are shown as logical flow diagrams, and each operation represents a sequence of operations that can be implemented in hardware, computer instructions, or a combination thereof. For example, the operations may be computer instructions provided by a computer system, such as computer systems 290 of FIGS. 2A and 2B and computer system 810 of FIG. 8. In the context of computer instructions, an operation represents computer-executable instructions stored on one or more computer-readable storage media that, when executed by one or more processors, perform the recited operations. Generally, computer-executable instructions include routines, programs, objects, components, data structures, etc. that perform a particular function or implement a particular data type. The order in which the operations are described is not intended to be construed as limiting, and any number of the described operations may be omitted, combined, or performed in any order and / or in parallel to implement the process.

[0044] Further, some, any, or all of the process may be executed under the control of one or more computer systems configured with executable instructions, and implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) collectively executed on one or more processors, by hardware, or a combination thereof. As described above, the code may be stored on a computer-readable storage media in the form of, for example, a computer program comprising a plurality of instructions executable by one or more processors. The computer-readable storage media is non-transitory.

[0045] Figure 4 shows an exemplary flowchart illustrating process 400 for adjusting the ratio of gas species in a gas mixture using a plasma source. Features ending with reference numbers similar to those discussed above are understood to be similar, except as otherwise described below. As noted above, any of the steps in this process may be instructions provided by a computer system. This adjustment can be performed in real time or before generating the plasma. Referring to step 410, a desired ion ratio may be provided to a computer system (e.g., computer system 290). For example, a user may desire an ion ratio of 70% oxygen and 30% xenon to mill a particular portion of a sample. Moving to step 420, the computer system may predict a gas mixture composition for use in conjunction with providing this desired ion ratio. For example, the computer system may predict that a gas mixture of 80% oxygen and 20% xenon can be used to achieve this desired ion ratio. It should be noted that the selected mixing ratio of the gases may not necessarily be converted to the same mixing ratio of ions due to multiple factors including physical and chemical effects within the chamber (e.g., RF power, temperature within the system, ionization efficiency of each gas, total pressure within the plasma chamber, generation of both atomic and molecular species such as O+ and O2+, or chemical interactions between the gases or between the gases and system components). In some examples, different systems can provide slightly different ion mixing ratios from the same gas mixture input.

[0046] This prediction may be based on a prediction model trained using machine learning techniques such as hidden Markov models, convolutional neural networks, polynomial regression, and cluster analysis. Training the prediction model may involve optimizing a loss function using various different optimization techniques such that the address risk model output closely tracks the actual fraud in the training set. Such optimization techniques can include gradient descent, backpropagation, conjugate gradient, other gradient techniques, or Hessian techniques such as Newton's method. The loss function can be the difference between the measured ion ratio and the predicted ion ratio at one or more time points. The prediction model can be a machine learning model trained using a large set of data including input parameters (e.g., gas mixture composition, RF power, total pressure of the gas mixture, etc.) and the resulting ion ratios. Thus, the prediction model can find patterns between the gas mixture and the ion ratio such that the prediction model can output a gas mixture composition predicted to produce a desired ion ratio. Alternatively, the prediction model can output a predicted ion ratio that may result from a particular gas mixture. In other embodiments, the prediction may be based on an estimation table that is pre-populated with estimated gas mixtures that would produce an estimated ion gas ratio. In some embodiments, the estimation table is specific to a particular system because each system may produce a different ion ratio output due to slight differences in plasma generation based on each hardware implementation.

[0047] The plasma source system can generate this predicted gas mixture. For example, referring to FIG. 2A, the controllers 240a, 240b can introduce at least one of the gas species from each of the gas reservoirs 230a, 230b into the corresponding capillary constrictions 250a, 250b such that each gas species has a partial pressure within the plasma source chamber 202 and can form the predicted gas mixture. Returning to FIG. 4, at step 430, this predicted gas mixture can be introduced into the plasma source chamber 202 within the plasma source tube 203. Moving to step 440, the gas mixture can be ionized to extract an ion beam from the gas mixture. Moving to step 450, the ion ratio can be measured by a measurement unit (e.g., the measurement unit 275 of FIGS. 2A and 2B). Further details regarding this measurement of the ion ratio can be found in U.S. Patent Application Publication No. 10,763,079, the content of which is hereby incorporated by reference in its entirety. The ion ratio can be measured continuously (e.g., once every millisecond, 1 second, 5 seconds, 10 seconds, 1 minute, etc.) to provide data regarding the measured ion ratio when the ion beam mills the sample. In this way, data regarding the measured ion ratio can be continuously provided to the computer system when the ion beam mills various layers of the sample and when adjustments are made to the ion beam to adjust the ion ratio. However, in other embodiments, the ion ratio may be measured only when commanded, such as when the user actively commands the computer system to measure the ion ratio.

[0048] Upon moving to step 460, the computer system can determine whether the ion ratio is correct. Specifically, the computer system can compare whether the measured ion ratio is substantially the same as the desired ion ratio input in step 410. The ion ratio can be substantially similar if the measured ion ratio value and the desired ion ratio value are within a deviation of about 20% of each other, for example, about 10% deviation, for example, about 5% deviation, or are exactly the same. If the ion ratio is substantially the same, the process (e.g., continuous extraction of the ion beam for milling the sample) can be continued in step 470.

[0049] If the measured ion ratios are not substantially similar, in step 480, one or more input parameters may be adjusted to achieve the desired ion ratio. For example, one or more gas species in the gas mixture can be adjusted to adjust the ion ratio. This can include adjusting the partial pressure of a particular gas species in the gas mixture to change the composition of the gas mixture, as described above. In some embodiments, an entire gas species can be replaced with another gas species (or completely removed from the gas mixture). The RF power may also be adjusted to change the ion ratio of the ion beam. The total pressure of the gas mixture within the plasma source chamber can be adjusted to affect the change in the ion ratio. In some embodiments, only one of these parameters can be adjusted, while in other embodiments, multiple parameters (e.g., all parameters) can be adjusted. Once the parameter(s) are adjusted, the ion beam can be extracted and the ion ratio can be measured again. The computer system can compare whether the new ion ratio is substantially the same as the desired ion ratio. The computer can repeat the above process as desired until the measured ion ratio is substantially the same as the desired ion ratio.

[0050] In any case, the measured ion ratios can be provided to the prediction model as additional data for use when updating the prediction model. For example, if the measured ion ratios are substantially the same as the desired ion ratios, the data regarding the measured ion ratios can be used to confirm the accuracy of the prediction model for these specific gas species (e.g., confirm that the parameters predicted by the prediction model provide an ion ratio substantially the same as the desired ion ratio). This may result in minimal or no change to the prediction model. If the measured ion ratios are not substantially similar to the desired ion ratios, the data regarding the measured ion ratios can be used to indicate that the prediction model for these specific gas species is not accurate. This may result in a change to the prediction model to account for this data so that future prediction models can provide measured ion ratios that more accurately correspond to the desired ion ratios (e.g., change the parameters predicted by the prediction model to provide the desired ion ratio). The prediction model may be updated in real time (e.g., updated when data is provided to the prediction model) or at a later date (e.g., updated when sufficient data has been collected before a new version of the prediction model is provided to the computer system).

[0051] In some examples, changes to a predictive model can be used to perform system health monitoring. A computer system can maintain a history of updates to the predictive model (e.g., in a storage device or in memory). When the system is in a steady state (i.e., healthy), the measured ion ratios are often substantially the same as the desired ion ratios, so the frequency of updates to the predictive model may be low. However, when one or more components of the system begin to degrade, the updates to the predictive model can become more frequent and / or the deviation between the measured ion ratios and the desired ion ratios can become larger. In some examples, the computer can analyze the history of updates to the predictive model to determine that the system may need service. When it is determined that the system needs service, the computer can notify the user to schedule service or to check the components of the system for degradation, for example, using a message on a graphical user interface on a monitor as described below in connection with FIG. 8.

[0052] FIG. 5 shows an exemplary flowchart illustrating a process 500 for mixing gases within a plasma source chamber. Features ending with reference numerals similar to those discussed above are understood to be similar, except as otherwise described below. For example, the flowchart of FIG. 5 can provide a more detailed process for step 430 of the flowchart shown in FIG. 4. The flowchart of process 500 is described with reference to the plasma source system 280 shown in FIG. 2A. As described above, any of the steps in this process may be instructions provided by a computer system. Moving to step 510, valves 231a, 231b may be opened to release gas from gas reservoirs 230a, 230b into gas supply lines 204a, 204b until a desired pressure (e.g., about 100 to 1000 millibars) is reached. Moving to step 520, controllers 240a, 240b may be opened to release each of the gases at a controlled rate or volume from gas supply lines 204a, 204b into capillary constrictions 250a, 250b. Each of controllers 240a, 240b can release gas from gas supply lines 204a, 204b into capillary constrictions 250a, 250b to achieve a desired gas mixture and ion ratio within plasma source chamber 202. Specifically, each of controllers 240a, 240b can release each of the gas species at an individualized pressure such that each gas species has a partial pressure within the gas mixture and thus achieves a specific gas mixture composition. As described above, this gas mixture within plasma source chamber 202 is then ionized to extract an ion beam for use in milling a sample.

[0053] FIG. 6 shows an exemplary flowchart illustrating process 600 for discharging gas from a plasma source. Features ending with reference numerals similar to those discussed above are understood to be similar, unless otherwise described below. The flowchart of FIG. 6 is described with reference to the plasma source system 280 shown in FIG. 2B. As described above, any of the steps in this process may be instructions provided by a computer system. Referring to step 610, the bypass manifold 252 can be separated from the plasma source tube 203 to partially discharge the plasma source system 280. In particular, the bypass actuator 242 can be actuated to move the bypass manifold 252 away from the plasma source tube 203. By separating the bypass manifold 252 from the plasma source tube 203, it becomes possible to discharge the gas in the capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 into the internal volume 262, which will then flow towards the vacuum source. This partially discharges the plasma source system 280 so that the gas in the capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 can be discharged without discharging the gas in the gas supply lines 204a, 204b, because the controllers 240a, 240b fluidly isolate the gas supply lines 204a, 204b from the capillary constrictions 250a, 250b. In some embodiments, moving to step 620, the controllers 240a, 240b open the relief port valves 244a, 244b to allow gas to be discharged from the capillary constrictions 250a, 250b at the first ends 251a, 251b, and the gas in the capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 can be discharged more rapidly. The plasma source system 280 can also open the pumps 222a, 222b and discharge the gas in the gas supply lines 204a, 204b at the first end and / or open the relief port valves 244a, 244b of the controllers 240a, 240b and discharge the gas in the gas supply lines 204a, 204b at the second end to be completely discharged.

[0054] FIG. 7 shows an exemplary flowchart of a process 500 for a computer system that provides instructions to a plasma source to mix gases. Features ending with reference numbers similar to those discussed above are understood to be similar, except as described below. The flowchart of FIG. 7 is described with reference to the charged particle system 200 shown in FIG. 2A. Moving to step 710, the computer system 290 may instruct the first controller 240a to open the first variable outlet pressure valve and release the first gas at a first flow rate from the first gas reservoir 230a through the first capillary constriction 250a into the plasma source chamber 202. Moving to step 720, the computer system 290 may instruct the second controller 240b to open the second variable outlet pressure valve and release the second gas at a second flow rate from the second gas reservoir 230b through the second capillary constriction 250b into the plasma source chamber 202. The second capillary constriction 250b may be separate from the first capillary constriction 250a. As described above, the gases can flow from the capillary constrictions 250a, 250b into the bypass chamber 254 and then into the plasma source chamber 202 before being ionized. In this way, the computer system 290 can facilitate the precise control of the partial pressures of each gas species from the gas reservoirs 230a, 230b to achieve a specific composition of the gas mixture.

[0055] To partially evacuate the charged particle system 200, the computer system 290 can also command the bypass actuator 242 to move the bypass manifold 252 away from the source tube 203 so that the first and second capillary constrictions 250a, 250b, the bypass chamber 254, and the plasma source chamber 202 are in fluid communication with a vacuum source. The computer system 290 can also open a first relief port valve 244a defined within the first controller 240a to fluidly couple the first capillary constriction 250a to the vacuum source, and open a second relief port valve 244b defined within the second controller 240b to fluidly couple the second capillary constriction 250b to the vacuum source.

[0056] Any of the computer systems referred to herein can utilize any suitable number of subsystems. Examples of such subsystems are shown in the computer system 810 of FIG. 8. In some embodiments, the computer system includes a single computer device and the subsystems can be components of the computer device. In other embodiments, the computer system can include a plurality of computer devices, each of which is a subsystem and has internal components. The computer system can include desktop and laptop computers, tablets, mobile phones, and other mobile devices.

[0057] The subsystems shown in FIG. 8 are interconnected via a system bus 875. Additional subsystems are shown such as a printer 874, a keyboard 878, storage device(s) 879, and a monitor 876 coupled to a display adapter 882 (e.g., a display screen such as an LED). Peripheral devices and input / output (I / O) devices coupled to the I / O controller 871 can be connected to the computer system by any number of means known in the art such as input / output (I / O) ports 877 (e.g., USB, FireWire (registered trademark)). For example, the computer system 810 can be connected to a wide area network such as the Internet, a mouse input device, or a scanner using the I / O port 877 or an external interface 881 (e.g., Ethernet (registered trademark), Wi-Fi, etc.). The interconnection via the system bus 875 enables the central processor 873 to communicate with each subsystem and control the execution of a plurality of instructions from the system memory 872 or storage device(s) 879 (e.g., a fixed disk such as a hard drive or an optical disk), as well as the exchange of information between subsystems. The system memory 872 and / or storage device(s) 879 can embody a computer-readable medium. Another subsystem is a data collection device 885 such as a camera, a microphone, an accelerometer, etc. Any of the data referred to herein can be output from one component to another and output to the user.

[0058] A computer system can include a plurality of identical components or subsystems that are connected together, for example, by an external interface 881, by an internal interface, or via a removable storage device that can be connected and removed from one component to another. In some embodiments, a computer system, subsystem, or device can communicate via a network. In such an example, one computer can be considered a client and another computer can be considered a server, and each can be part of the same computer system. The client and server can each include a plurality of systems, subsystems, or components.

[0059] Aspects of embodiments can be implemented in the form of control logic using a hardware circuit (e.g., an application specific integrated circuit or a field programmable gate array) and / or using computer software stored in a memory having a processor that is generally programmable in a modular or integrated fashion. Thus, the processor can include a memory storing software instructions that configure the hardware circuit, as well as an FPGA or ASIC having configuration instructions. As used herein, a processor can include a single-core processor, a multi-core processor on the same integrated chip, or a plurality of processing units on a single circuit board or networked, as well as dedicated hardware. Based on the disclosure and teachings provided herein, one of ordinary skill in the art will know and understand other ways and / or means for implementing embodiments of the present disclosure using hardware and combinations of hardware and software.

[0060] Any of the software components or functions described in this application, such as processes 400, 500, 600, or 700, can be implemented as software code executed by a processor using, for example, conventional or object-oriented techniques and any suitable computer language, such as Java (registered trademark), C, C++, C#, Objective-C, Swift, or a scripting language such as Perl or Python. The software code can be stored as a series of instructions or commands on a computer-readable medium for storage and / or transmission. Suitable non-transitory computer-readable media can include random access memory (RAM), read-only memory (ROM), magnetic media such as a hard drive or floppy disk, or optical media such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray disc, flash memory, and the like. The computer-readable media can be any combination of such devices. Further, the order of operations can be rearranged. The process can end when its operations are completed, but can have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subprogram, and the like. When the process corresponds to a function, its end can correspond to the return of that function to the calling function or main function.

[0061] Such a program may also be encoded and transmitted using a carrier signal adapted for transmission via various protocols-compliant wired, optical, and / or wireless networks, including the Internet. Thus, a computer-readable medium can be created using a data signal encoded with such a program. A computer-readable medium encoded with program code may be packaged with a compatible device or provided separately from other devices (e.g., via an Internet download). Any such computer-readable medium may exist on or within a single computer product (e.g., a hard drive, a CD, or an entire computer system) or on or within different computer products within a system or network. A computer system may include a monitor, a printer, or other suitable display for providing any of the results referred to herein to a user.

[0062] Any of the methods described herein can be performed in whole or in part using a computer system that includes one or more processors configured to perform the steps. Any operations performed using the processor (e.g., sorting, determining, comparing, computing, calculating) can be performed in real time. The term "real time" can refer to a computing operation or process that is completed within a particular time constraint. The time constraint can be one minute, one hour, one day, or seven days. Thus, embodiments can potentially be directed to a computer system configured to perform any of the steps of the methods described herein using different components that each perform a respective step or respective group of steps. Although presented as numbered steps, the steps of the methods herein can be performed simultaneously, at different times, or in a different order. Additionally, some of these steps can be used in conjunction with some of the steps from other methods. Also, all or some of the steps can be optional. Further, any of the steps of the methods can be performed using a system module, unit, circuit, or other means for performing these steps.

[0063] In the foregoing specification, embodiments of the present disclosure have been described with reference to numerous specific details that may vary from embodiment to embodiment. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the present disclosure and what the applicant intends the scope of the present disclosure to be is the literal and equivalent scope of the set of patent claims issued from this application in the specific form in which such patent claims are issued, including any subsequent amendments thereof. The specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure.

[0064] In addition, spatially relative terms such as "lower" or "upper" can be used to describe, for example, the relationship of an element(s) and / or feature(s) to another element and / or feature as shown in the figures. It will be understood that spatially relative terms are intended to encompass different orientations of the device in use and / or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as the "bottom" surface can then be oriented "above" other elements or features. The device can be oriented differently (e.g., rotated at 90 degrees or other orientations), and the spatially relative descriptors used herein can be interpreted accordingly.

[0065] The terms "and", "or", and "and / or" as used herein can include a variety of meanings that are also expected to depend at least in part on the context in which such terms are used. Typically, for "or", when used to associate a list such as A, B, or C, herein it is intended to mean A, B, and C in an inclusive sense and A, B, or C in an exclusive sense as used herein. In addition, the term "one or more" as used herein can be used to describe any singular feature, structure, or property or can be used to describe some combination of features, structures, or properties. However, it should be noted that this is merely an illustrative example and the claimed subject matter is not limited to this example. Further, the term "at least one of" when used to associate a list such as A, B, or C can be interpreted to mean any combination of A, B, C, AB, AC, BC, AA, AAB, ABC, AABBCCC, etc., of A, B, and / or C.

[0066] References throughout this specification to "an example", "example", "a specific example", or "exemplary embodiment" mean that a particular feature, structure, or characteristic described in connection with the feature and / or example may be included in at least one feature and / or example of the claimed subject matter. Accordingly, appearances throughout this specification of the phrases "in one example", "in an example", "in a specific example", "in a particular embodiment", or other similar phrases are not necessarily all referring to the same feature, example, and / or limitation. Further, the particular features, structures, or characteristics may be combined in one or more examples and / or features.

[0067] In some embodiments, an operation or process may involve a physical manipulation of a physical quantity. Usually, though not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transmitted, combined, compared, or otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals, etc. It should be understood, however, that all of these or similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, as will be apparent from the discussion herein, throughout this specification, discussions utilizing terms such as "processing", "computing", "calculating", "determining", etc., refer to the operations or processes of a special purpose computer, a special purpose computing device, or similar special purpose electronic computing devices. Thus, in the context of this specification, a special purpose computer or similar special purpose electronic computing device can operate on or transform signals typically represented as physical electronic or magnetic quantities within the memory, registers, or other information storage devices, transmission devices, or display devices of the special purpose computer or similar special purpose electronic computing device.

[0068] In the foregoing detailed description, numerous specific details have been set forth in order to provide a thorough understanding of the claimed subject matter. However, it will be understood by those skilled in the art that the claimed subject matter may be practiced without these specific details. In other instances, well-known methods and devices that would be known to those skilled in the art have not been described in detail so as not to obscure the claimed subject matter. Accordingly, the claimed subject matter is not intended to be limited to the specific examples disclosed, but rather such claimed subject matter is also intended to include all aspects falling within the scope of the appended claims, and their equivalents.

Claims

1. An ion beam system, comprising: a plasma source tube defining a plasma source chamber; a first gas reservoir containing a first gas and a second gas reservoir containing a second gas; a first controller fluidly coupled to the first gas reservoir and configured to control a first flow rate of the first gas, and a second controller fluidly coupled to the second gas reservoir and configured to control a second flow rate of the second gas; a first capillary constriction including a first end fluidly coupled to the first controller and a second end fluidly coupled to the plasma source chamber, and a second capillary constriction including a third end fluidly coupled to the second controller and a fourth end fluidly coupled to the plasma source chamber, wherein the first capillary constriction and the second capillary constriction are separate from each other. The ion beam system.

2. The ion beam system according to claim 1, wherein the first capillary constriction and the second capillary constriction are separated from each other.

3. The ion beam system according to claim 1, wherein the first capillary constriction and the second capillary constriction do not intersect each other.

4. The ion beam system according to claim 1, wherein at least one of the first controller or the second controller includes a variable outlet pressure valve.

5. The ion beam system according to claim 1, further comprising a first gas supply line fluidly coupling the first gas reservoir and the first controller, and a second gas supply line fluidly coupling the second gas reservoir and the second controller, wherein the first controller is configured to fluidly isolate the first gas supply line from the first capillary constriction, and the second controller is configured to fluidly isolate the second gas supply line from the second capillary constriction.

6. The ion beam system according to claim 1, further comprising a bypass manifold coupled to the plasma source tube, wherein the bypass manifold defines a bypass chamber in fluid communication with the plasma source chamber. The second end of the first capillary constriction is coupled to the bypass manifold, and the fourth end of the second capillary constriction is coupled to the bypass manifold, the ion beam system according to claim 1. **Claim 7** In a first state, the bypass manifold is coupled to the plasma source tube, and the first and second capillary constrictions, the bypass chamber, and the plasma source chamber are fluidly isolated from a vacuum source. In a second state, the bypass manifold is spaced from the plasma source tube, and the first and second capillary constrictions, the bypass chamber, and the plasma source chamber are in fluid communication with the vacuum source, the ion beam system according to claim 6. **Claim 8** The ion beam system according to claim 7, further comprising a chamber body defining an internal volume housing the plasma source tube and the bypass manifold, the internal volume being in fluid communication with the vacuum source. **Claim 9** The first controller includes a first relief port valve fluidly coupled to the vacuum source, and the second controller includes a second relief port valve fluidly coupled to the vacuum source. In the second state, the first controller is configured to fluidly couple the first capillary constriction to the first relief port valve, and the second controller is configured to fluidly couple the second capillary constriction to the second relief port valve, the ion beam system according to claim 7. **Claim 10** An ion beam system, a plasma source tube defining a plasma source chamber, a first gas reservoir containing a first gas species and a second gas reservoir containing a second gas species, a first controller fluidly coupled to the first gas reservoir and configured to control a first flow rate of the first gas species, a first capillary constriction including a first end fluidly coupled to the first controller and a second end fluidly coupled to the plasma source chamber, and a computer system in communication with the first controller and configured to provide instructions for operating the first controller. **Claim 11** a second controller fluidly coupled to the second gas reservoir and configured to control a second flow rate of the second gas species; a second capillary constriction including a third end fluidly coupled to the second controller and a fourth end fluidly coupled to the plasma source chamber, the first capillary constriction and the second capillary constriction being separated from each other, the ion beam system of claim 10, further comprising a second capillary constriction. **Claim 12** The ion beam system of claim 10, wherein the first controller includes a variable outlet pressure valve. **Claim 13** The ion beam system of claim 10, further comprising a first gas supply line fluidly coupling the first gas reservoir and the first controller, the first controller being configured to fluidly isolate the first gas supply line from the first capillary constriction. **Claim 14** The ion beam system of claim 10, further comprising a bypass manifold coupled to the plasma source tube, the bypass manifold defining a bypass chamber in fluid communication with the plasma source chamber, the second end of the first capillary constriction being coupled to the bypass manifold, the ion beam system of claim 10. **Claim 15** In a first state, the bypass manifold is coupled to the plasma source tube, and the first capillary constriction, the bypass chamber, and the plasma source chamber are fluidly isolated from a vacuum source, In a second state, the bypass manifold is spaced from the plasma source tube, and the first capillary constriction, the bypass chamber, and the plasma source chamber are in fluid communication with the vacuum source, the ion beam system of claim 14. **Claim 16** The ion beam system of claim 15, further comprising a chamber body defining an internal volume housing the plasma source tube and the bypass manifold, the internal volume being in fluid communication with the vacuum source. **Claim 17** The first controller includes a first relief port valve fluidly coupled to the vacuum source, In the second state, the first controller is configured to fluidly couple the first capillary constriction to the first relief port valve, the ion beam system of claim 15. **Claim 18** A non-transitory computer-readable storage medium storing computer-readable instructions of a program, wherein when the instructions are executed by one or more computing devices, the one or more computing devices are caused to open a first variable outlet pressure valve and command a first controller to discharge a first gas from a first gas reservoir through a first capillary constriction into a plasma source chamber defined in a plasma source tube at a first flow rate; open a second variable outlet pressure valve and command a second controller to discharge a second gas from a second gas reservoir through a second capillary constriction into the plasma source chamber at a second flow rate so that the first and second gases are mixed in the plasma source chamber, the second capillary constriction being separate from the first capillary constriction, the non-transitory computer-readable storage medium causing the operations to be performed.

19. The first gas and the second gas are each discharged from the first capillary constriction and the second capillary constriction into a bypass chamber defined in a bypass manifold. The bypass manifold is coupled to the plasma source tube. The bypass chamber is fluidically isolated from a vacuum source. The operations further include commanding a bypass actuator to move the bypass manifold away from the plasma source tube so that the first and second capillary constrictions, the bypass chamber, and the plasma source chamber are in fluid communication with the vacuum source. The non-transitory computer-readable storage medium according to claim 18.

20. The operations further include opening a first relief port valve included in the first controller to fluidically couple the first capillary constriction to the vacuum source and opening a second relief port valve included in the second controller to fluidically couple the second capillary constriction to the vacuum source. The non-transitory computer-readable storage medium according to claim 19.

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