Grid surface conditioning for ion beam systems

Abstract

In-situ cleaning of multiple grids in an ion beam system, such as a deposition / etching system, involves applying a negative bias to the most downstream grid and etching away redeposited material from the grid. Any or all of the system chamber pressure, ion beam source extraction current, beam divergence angle, and perveance can be adjusted using a decelerating grid bias. The disclosed method can be applied to any gridded ion source system, including those using an assisted ion beam.

Description

[Background technology]

[0001] In plasma ion beam applications (either or both ion beam deposition and ion beam etching), the returned sputtered material is deposited and builds up on the downstream surface of the grid. Over time, the spalling or flaking of the sputtered material can cause premature failure of the grid, which in turn can lead to arcing and / or defects in the grid. Summary of the Invention

[0002] The present disclosure relates to in situ cleaning of multiple grids in an ion deposition / etching system, which involves applying a negative bias to the most downstream grid and etching away redeposited material from the grid. Any or all of the system chamber pressure, extraction current in the ion beam source, beam divergence, and perveance can be adjusted using grid bias. The disclosed method can be applied to any gridded ion source system, including those using an assisted ion beam.

[0003] The method is particularly suited to ion beam systems or sources operating at high pressures, high powers, and high sputtering rates. Under these conditions, large amounts of sputtered material typically accumulate on the grid being etched or deposited, resulting in a shorter lifespan and the need for more frequent maintenance, thereby reducing system uptime and operational efficiency and ultimately increasing the system's cost of ownership. Use of the method described herein reduces system downtime, improving productivity and reducing operating costs. The method can be performed during or between substrate processing.

[0004] In one particular embodiment, the present disclosure describes a method for conditioning a deceleration grid in an ion beam system by applying a negative bias to the grid and delivering a wide, defocused ion beam through the negatively biased deceleration grid to etch away redeposited material from the deceleration grid.

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. These and various other features and advantages will become apparent from the following Detailed Description. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic side view of a portion of an ion beam deposition system. [Figure 2] FIG. 2 is a schematic side view of three grids from an ion beam deposition system. [Figure 3] FIG. 3 is a flow chart of an exemplary step-by-step method for conditioning a grid. [Figure 4A] FIG. 4A is an optical micrograph of the conditioned grid. [Figure 4B] FIG. 4B is an optical micrograph of the conditioned grid. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present disclosure relates to a method for in situ cleaning and conditioning in an ion beam system, such as an ion deposition system. The method provides a conditioning process for one or more grids by gradually etching the surface of the grids, removing deposited material from the grids' surfaces, and reducing the risk of system contamination due to peeling and / or flaking of any redeposited material. The method also provides a texturing process for the one or more grids to increase surface roughness. The method uses a negatively biased grid, typically a decelerating grid closest to the sputter target, which is usually grounded during system operation. The negatively biased grid, combined with increased chamber pressure and / or beam expansion, removes redeposited material from the one or more grids. This extends the life of the one or more grids and improves system throughput.

[0008] The method can be applied to multiple sources with two or more grids. Most ion sources use three grids, which are referred to in order from upstream to downstream in the plasma direction as a screen grid / acceleration grid / deceleration grid, or a screen grid / acceleration grid / deceleration grid, or a beam grid / suppressor grid / ground grid.

[0009] In this method, charge-exchange ions near a negatively biased decelerating grid are increased, e.g., maximized, accelerated toward the grid surface, impacting the surface and etching away material from the grid surface. During these controlled etching procedures, no detrimental effects are caused to the grid or grids. Optical parameters of the grids, such as hole / aperture diameter, plate thickness, and grid spacing, are essentially unaffected and no measurable changes in dimensions occur.

[0010] The cleaning methods described herein are performed under controlled parameters as described, while maintaining vacuum in the system, and do not result in particles or other solid contaminants being shed from the grid that contaminate the deposition system. In fact, the material etched off the grid is the same material that is deposited on the substrate, thereby maintaining the overall cleanliness of the deposition system.

[0011] Since there is no need to break the system vacuum, system downtime is reduced. Conditioning can be performed during or between substrate processing. Additionally, periodic in situ grid conditioning by these methods can significantly extend the mean time between more extensive system maintenance as well as prevent unplanned system shutdowns due to contamination. Conditioning the grid at regular intervals eliminates ambiguity in determining the best time to perform maintenance, as the thickness of redeposited material can be controlled and maintained below a desired level.

[0012] The disclosed method can be applied to any gridded ion source, including those using an assisted ion beam. The method is particularly suited to ion systems or sources operating at high pressures, high powers, and high sputtering rates. Under these conditions, large amounts of sputtered material typically accumulate on the etched or deposited grids, shortening their lifespan and requiring more frequent maintenance, thereby reducing system uptime and operational efficiency and ultimately increasing the system's cost of ownership.

[0013] Traditionally, grid plates have been conditioned / cleaned ex situ by sand / bead blasting, chemical etching, or laser treatment. It is also known to coat the grid surface with a protective layer with a predictable erosion rate to control buildup. Because the stress and critical thickness before delamination or flaking occur are specific properties of the material, both such conditioning and coating techniques need to be customized for each different sputtered material. Furthermore, both techniques require breaking the vacuum of the ion beam system, and interrupting the operation of the deposition / etching system to treat the grid ex situ increases the cost of ownership. Therefore, traditional methods require different types of grid surface treatments and / or coatings depending on the sputter target material, e.g., metallic or insulating, e.g., high or low adhesion, all of which reduce system productivity. The in situ cleaning method described herein increases uptime, improves productivity, and reduces operating costs.

[0014] In the following description, reference is made to the accompanying drawings, which form a part of this specification, and in which at least one specific implementation is shown by way of example. The following description provides additional specific implementations. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. Therefore, the following detailed description should not be taken in a limiting sense. The disclosure is not so limited, but an understanding of various aspects of the disclosure will be gained through the description of examples, including the drawings, provided below. In some instances, a reference number may have an associated sub-label consisting of a lower case letter to indicate one of multiple similar components. When a reference number is made without specifying a sub-label, the reference is intended to refer to all such multiple similar components.

[0015] 1 shows a schematic diagram of an ion beam system 100. While an embodiment of the ion beam system 100 is shown as an ion beam sputtering deposition system, components of the ion beam system 100 may also be used, with some modifications, to implement any or all of an ion beam etching system, an ion implantation system, an ion beam deposition system, an ion beam assisted deposition system, etc. System 100 may be used, for example, to deposit, deposit and modify, and / or deposit and etch materials.

[0016] The ion beam system 100 includes an ion beam source 102, a target assembly 104, and a substrate assembly 106 for supporting a substrate 116. The substrate assembly 106 may include a single large substrate 116, as shown in Figure 1, or may include a subassembly holder that holds multiple individual smaller substrates 116. The substrate 116 may be formed from, for example, one or more layers of silicide(s), nitride(s), oxide(s), metal(s) including alloys, or ceramic(s).

[0017] The ion beam source 102 generates an ion beam 120, which may include multiple ion beamlets directed toward a target assembly 104. The target assembly 104 includes at least one target 114 mounted thereon, the at least one target 114 including a material desired to be deposited on a substrate 116. The ion beam 120 has a centerline axis 125 aimed or oriented toward the target 114 so that the ion beam 120 completely or nearly completely impacts the target 114. The target 114 is positioned on a platform of the target assembly 104 that can rotate the target 114 about the given axis 115 as needed. In some designs, the target 114 may be tilted. When the ion beam 120 impacts the target 114, it generates a sputter plume 140 of material from the target 114.

[0018] Examples of materials for the target 114 include, but are not limited to, metals such as titanium (Ti), tungsten (W), molybdenum (Mo), tantalum (Ta), ruthenium (Ru), cobalt (Co), copper (Cu), and rhodium (Rh); metal and semiconductor nitrides such as, but not limited to, titanium nitride (TiN), tantalum nitride (TaN), silicon nitride (SiN), molybdenum nitride (MoN), and tungsten nitride (WN, WN, WN); metal and semiconductor oxides such as silicon oxide (SiO), titanium oxide (TiO), and aluminum oxide (AlO); metal and semiconductor silicides such as tungsten silicide (WSi), molybdenum silicide (MoSi), and titanium silicide (TiSi), as well as other types of metal targets, dielectric targets, and semiconductor targets.

[0019] The ion beam 120 strikes the target 114 at an angle such that a sputter plume 140 generated from the target 114 travels toward the substrate assembly 106 and the substrate 116. In some configurations of the ion beam system 100, the sputter plume 140 may diverge as it travels from the target 114 toward the substrate assembly 106, causing it to partially overspray the substrate 116. However, in other configurations, the sputter plume 140 may be made more or less concentrated so that the resulting material deposition can be more effectively distributed over specific areas of the substrate 116.

[0020] The substrate assembly 106 is positioned and oriented so that the sputter plume 140 also impacts the substrate 116 at a desired angle. In a particular exemplary configuration of the ion beam system 100, the substrate assembly 106 is mounted in a fixture 118 that allows the substrate assembly 116 to be moved in a desired manner, including rotating the substrate assembly 106 about its axis 119 or pivoting the fixture 118 to tilt the substrate 106 to change its angle relative to the sputter plume 140.

[0021] In one example of the ion beam system 100, the ion source 102 produces positively charged ions. However, in another example, the ion source 102 produces negatively charged ions. The remainder of the disclosure herein will assume that the ions produced by the ion source 102 are positively charged. The ion source 102 can be a DC, radio frequency (RF), or microwave type gridded ion source.

[0022] The system 100 may include one or more grids 110 proximate the ion beam source 102 to direct the ion beam 120 from the ion beam source 102 to the target assembly 104. In a particular configuration of the ion beam system 100, the one or more grids 110 steer the ion beamlets such that the ion beam 120 is more divergent from a centerline axis 125 of the ion beam source 102 than would be the case if bulk ion beam steering were not provided. In another configuration, the one or more grids 110 steer the ion beamlets such that the ion beam 120 does not diverge from the centerline axis 125. Other structures and configurations may also be provided. The one or more grids 110 can cause the ion beam 120 to have a symmetric or asymmetric cross-sectional profile about the beam axis.

[0023] The one or more grids 110 have multiple holes or openings therethrough to allow multiple beamlets of the ion beam 120 to pass through the one or more grids 110. The individual holes in the one or more grids 110 can be arranged to maximize the density of holes per area to maximize ions extracted from the ion source 102. The one or more grids 110 can have a pattern of linear holes or elliptical holes.

[0024] As noted above, the illustrated system 100 is a general-purpose system that may include any number of additional features, such as reactive gas sources, assist ion sources, assist gas sources, various heaters, neutralizers, turrets for multiple rotating targets, and diagnostic probes and sensors.

[0025] The system 100 can be operated under any operating conditions and at any conventional operating parameters. For example, the system 100 can be placed under an inert atmosphere, and reactive and / or noble gases can be added. For example, the gas introduction rate can range from a minimum of 1 sccm to a maximum of 100 sccm. The system 100 is typically operated at 10 -3 Less than 1×10 torr, e.g., -5 ~1×10 -3 The system 100 operates at a process (chamber) pressure of 100 Å / min. The system 100, and in particular the ion beam source 102, can utilize a high-energy ion beam having a voltage ranging from, for example, 40 V to 2000 V. The system can provide net deposition rates in excess of 10 Å / min, and in some cases, in excess of 100 Å / min.

[0026] 2 illustrates an exemplary grid assembly 200 for use in an ion beam system such as system 100. In this configuration, grid assembly 200 includes an ion source 202 and a target 204 with at least one grid disposed therebetween. Specifically, assembly 200 has three grids shown in cross section: a screen grid 210, an acceleration grid 220, and a deceleration grid 230; however, it should be understood that different combinations of grids may be used, including, but not limited to, configurations having a greater or lesser number of grids. In a particular configuration, one or more grids are flat and circular in shape, each having a substantially similar diameter, although other shapes are contemplated, including concave or convex dish shapes.

[0027] As shown in Figure 2, three grids 210, 220, and 230 are arranged parallel to one another with equal distances between the grids. While one or more grids are shown arranged parallel and equidistant from one another, this configuration is not required; for example, in some configurations, the distance between the first two grids is less than the distance between the last two grids. The grids 210, 220, and 230 have corresponding arrays of holes, with three holes shown in Figure 2 for each grid 210, 220, and 230.

[0028] The grids 210, 220, and 230 are positioned such that the screen grid 210 forms the downstream boundary of the discharge chamber of the ion beam source 202. The discharge chamber generates a plasma (e.g., from a noble gas such as argon or from a non-noble gas such as oxygen, nitrogen, or methane), and the grids 210, 220, and 230 extract ions from the plasma through multiple holes in the grids and accelerate them toward the target 204. The ions from the ion source 202 are organized into an ion beam consisting of multiple beamlets, each beamlet consisting of ions accelerating through a respective set of corresponding holes in the grids 210, 220, and 230.

[0029] In reality, individual ions of each beamlet flow through holes in the screen grid 210 along approximately the central axis, with a distribution across the aperture area of ​​the hole. Ions of multiple beamlets continue to accelerate toward the acceleration grid 220, flooding through corresponding holes in the acceleration grid 220 along approximately the central axis. Momentum imparted to the beamlet ions by the electric field between the screen grid 210 and the acceleration grid 220 then allows the beamlet ions to travel approximately along the central axis through holes in the deceleration grid 230 with a distribution across the aperture area of ​​the hole toward the target 204 located downstream.

[0030] Each of the grids 210, 220, 230 is operatively connected to a voltage source to independently apply a voltage bias to each of the grids 210, 220, 230. Screen grid 210 is closest to ion source 202 and is therefore the first grid to receive the ejection of ions from the discharge chamber. Screen grid 210 is therefore located upstream of acceleration grid 220 and deceleration grid 230. Screen grid 210 is marked with a plus (+) sign to indicate that screen grid 210 is positively charged or biased.

[0031] The acceleration grid 220 is positioned immediately downstream of the screen grid 210 in Figure 2. Thus, the acceleration grid 220 is downstream of the ion source 202 and the screen grid 210, and upstream of the deceleration grid 230. The acceleration grid 220 is marked with a minus (-) sign to indicate that the acceleration grid 220 is negatively charged or negatively biased. Applying a negative bias to the acceleration grid 220 causes ions to be drawn from the plasma and pass through the multiple holes in the screen grid 210.

[0032] 2, the deceleration grid 230 is positioned immediately downstream of the acceleration grid 220. Thus, the deceleration grid 230 is downstream of the ion source 202, the screen grid 210, and the acceleration grid 220, and upstream of the target 204. The deceleration grid 230 is typically grounded.

[0033] 2 shows three ions 241, 242, and 243 passing through adjacently arranged holes in the three grids 210, 220, and 230 and impacting the surface of the target 204. However, it should be understood that the three ions 241, 242, and 243 generally represent the distribution of ions flowing through the holes in the three grids 210, 220, and 230.

[0034] As the ions pass through the multiple holes in the deceleration grid 230, they collide with a sputter target 204 located downstream. When the ions collide with the surface of the target 204, a quantity of material from the target 204 breaks off from the surface of the target 204 and travels as plumes toward another workpiece, such as a substrate (not shown), which are shown as plumes 251, 252, and 253.

[0035] Additionally, some material from target 204 essentially generates plumes that return downstream of deceleration grid 230, possibly onto acceleration grid 220, and even partially onto screen grid 210; these return plumes are shown as plumes 261, 262, and 263. Material from plumes 261, 262, and 263 impinges on and deposits on the downstream side of deceleration grid 230, but may also deposit downstream of grids 210 and 220, and upstream of grids 210, 220, and 230.

[0036] As the thickness of the material downstream of the grids 210, 220, 230 increases, the likelihood of the material peeling or flaking increases, which can create particulate contamination within the chamber. To prevent the redeposited material from flaking and creating possible particulate contamination and potential arcing, the material is etched away in-situ by the system. This etching or conditioning of the redeposited material can occur on a periodic schedule (e.g., every 100 cycles, every 500 cycles), or can be scheduled to occur when the material is estimated or identified (e.g., measured) to a predetermined thickness.

[0037] A negative bias is applied to the grid 230 while ions are supplied from the ion beam source 202 to etch away redeposited material from the downstream side of the grid 230 and from the grids 210 and 220. The negative bias on the grid 230 attracts charge-exchange ions generated downstream of the grid 230 (between the grid 230 and the target 204), thereby etching or conditioning the surface of the grid 230.

[0038] The negative bias is based on, and varies based on, for example, the deposited and / or etched material, the deposition and / or etch rate, and the deposition and / or etch process. The negative bias applied to the grid 230 can range, for example, from 50 V to 600 V, to 700 V, to 800 V, or even to 1000 V.

[0039] The negative bias can be applied for a time measured in seconds or minutes, and can be as short as 5 seconds or as long as 3 hours (180 minutes). Examples of times include 10 seconds, 30 seconds, 45 seconds, 1 minute, 2 minutes, 5 minutes, 10 minutes, 30 minutes, 45 minutes, 60 minutes, 120 minutes, 180 minutes, and any time in between. The negative bias can be applied continuously, or in pulses, steps, or oscillatory fashion (e.g., between 50 V and 500 V at 10-second intervals).

[0040] An exemplary set of conditioning parameters includes 700V (screen grid voltage), 500V (acceleration grid voltage), 450mA (beam current), and 500V (deceleration grid voltage—negative bias) for 15 minutes.

[0041] In addition to applying a negative bias to the grid, one or more system parameters may be adjusted, such as the system chamber pressure, the extraction current of the ion beam source, or the R value (a measure that controls the beam divergence angle, where R is the screen grid voltage / (screen grid voltage + accelerating grid voltage), i.e., R = V), depending on the type of conditioning the system requires. s / (V s +V a ) and perveance (which determines the space charge limit of each hole or opening in the grid), any or all of these parameters can be increased or decreased.

[0042] FIG. 3 shows a generalized method 300 for conditioning a grid in an ion beam system. In a first step 302, the bias of the deceleration grid is switched from neutral or ground to negative. In a second step 304, the ion beam is changed from a highly focused beam to a wide, defocused beam. In a third step 306, one or more of the chamber pressure, ion beam source extraction current, R value, and perveance are adjusted. In a fourth step 308, material on the deceleration grid is etched away from at least the backside (downstream side), and possibly also from the frontside (upstream side). The etch rate varies at multiple locations on the deceleration grid and other grids and can be adjusted by parameters.

[0043] In a particular example experiment, a tungsten (W) target was placed in the ion beam system. Tungsten material was deposited on a witness sample to a thickness of 180 Å at a first test location and to a thickness of 216 Å at a second test location, where the beam parameters were V s =650V, V a = 250V, and the extracted current is I b = 450mA, and the voltage of the deceleration grid is Vd = -340 and the treatment time was 15 minutes. An average etching rate of 10 Å / min was achieved.

[0044] Another example of conditioning the grid is V d A negative bias of -500 V was applied for 5 minutes. The screen grid voltage was increased to 700 V, the accelerating grid voltage was increased to 450 V, and the extraction current was I b = 600 mA. An average etch rate of 33 Å / min was achieved against the retarding grid.

[0045] Figures 4A and 4B show two photographs of a deceleration grid conditioned according to the methods described herein, focusing on the holes present through the grid, with Figure 4A being an enlarged portion of Figure 4B. Examination of the conditioned grid reveals that the areas around the holes are not etched and no change in hole diameter is observed, but a pit and groove texture is observed on the grid, which may further improve grid life.

[0046] In Figures 4A and 4B, the hexagonal pattern indicates the etched area, with the corners of the hexagon being the deepest. The location of the hexagon center relative to the centerline of the hole is an indication of the alignment of the holes in the grids. If the hexagon center and the hole exactly overlap, the holes in the grids are perfectly aligned; if not, some misalignment exists in the grids. Thus, in addition to cleaning the deceleration grid, this method can provide feedback for complex grid designs to align or offset holes on the grids (e.g., screen grid, acceleration grid, and deceleration grid).

[0047] As shown, the specific operating parameters of the conditioning process are determined by the conditions and parameters of the ion beam process (e.g., deposition and / or etching) itself. A skilled operator of the ion beam system can determine the desired conditioning parameters for a particular deposition material based on the deposition parameters.

[0048] Grid conditioning by these processes, which apply a negative bias to the decelerating grid, offers many advantages. Grid conditioning can extend grid life in situ without the need to break the vacuum of the system. The risk of grid-borne contamination is greatly reduced, and in some cases eliminated. The conditioning process is applicable to any gridded ion source system and is material independent.

[0049] In addition to conditioning the grids (removing redeposited material) as described herein, one or more of the grids can be textured or seasoned by applying a negative bias to the most downstream grid. Texturing is a well-known method for extending the life of deceleration grids by roughening their surfaces. The roughening process creates random variations in the morphology of the grid surface, creating a pattern / texture on that surface. One technique for texturing grids is with a laser, where a fine pattern / texture is created on the downstream surface of the grid by moving the laser in a predetermined manner. Such a texturing process requires breaking the system vacuum and is performed ex-situ.

[0050] Similar to the grid conditioning described above, in-situ grid texturing can be achieved by applying a negative bias to the grid. A pit and groove (e.g., hexagonal) pattern is formed on the grid surface around the grid's holes, effectively functioning as the grid's texture. The morphology of the pit and groove pattern is controllable and depends on any or all of the bias voltage, extraction current, process pressure, R value, and perveance.

[0051] The description herein is based on having three grids in the system: a screen grid, an acceleration grid, and a deceleration grid, with the deceleration grid being the most downstream and closest to the target. However, the conditioning methods described herein can be used in systems with any number of grids, with the negative bias applied to the most downstream grid closest to the target.

[0052] The above specification and examples provide a complete description of the process and use of exemplary implementations of the present invention. The above description provides a specific implementation. It should be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. Therefore, the above detailed description should not be construed in a limiting sense. Features and elements from a particular implementation or embodiment may be readily applied to different implementations or embodiments. The present disclosure is not so limited, but an understanding of various aspects of the present disclosure will be gained through the description of the provided examples.

[0053] Unless otherwise indicated, all numerical values ​​expressing size, quantities, and physical properties of features should be understood as modified by the term "about." Accordingly, unless otherwise indicated, the numerical parameters set forth are approximations that may vary depending upon the desired properties sought to be obtained by one of ordinary skill in the art using the teachings disclosed herein.

[0054] As used herein, the singular forms "a," "an," and "the" include implementations having plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates otherwise.

[0055] As used herein, spatially related terms, including but not limited to "lower," "upper," "beneath," "below," "above," "on top," etc., are utilized for ease of description to describe the spatial relationship of an element to another element. Such spatially related terms encompass different orientations of the device in addition to the specific orientation shown in the figures and described herein. For example, if a structure shown in the figures were flipped or turned over, portions previously described as being below or below other elements would now be above or above those other elements.

[0056] Because many implementations of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Furthermore, structural features of different implementations may be combined in yet other implementations without departing from the scope of the described claims.

Claims

1. 1. A method for conditioning a grid in an ion beam system, comprising: applying a negative bias to a most downstream grid in the ion beam system; providing a wide, defocused ion beam through the negatively biased, most downstream grid; and etching away redeposited material from said most downstream grid.

2. adjusting the pressure in a chamber of the ion beam system; adjusting an extraction current of the ion beam system; adjusting the R value of the ion beam system; and adjusting the perveance of the ion beam system.

3. The method of claim 2 , comprising increasing one or more of the pressure, the extraction current, the R-value, and the perveance.

4. The method of claim 2 , comprising decreasing one or more of the pressure, the extraction current, the R-value, and the perveance.

5. 10. The method of claim 1, wherein applying a negative bias comprises applying a negative voltage of 50V to 800V for at least 30 seconds.

6. 6. The method of claim 5, wherein applying a negative voltage is performed for a maximum of 180 minutes.

7. The method of any one of claims 1 to 6, performed without opening the ion beam system during substrate processing.

8. The method of any one of claims 1 to 6, performed without removing the most downstream grid from the ion beam system.

9. 1. A method for in-situ conditioning of a grid in a chamber of an ion beam system after processing a substrate, said method being performed at varying chamber pressures, extraction currents, R-values, and perveances; applying a negative bias to a grid in the ion beam system; adjusting one or more of the chamber pressure, the extraction current, the R-value, and the perveance; and directing an ion beam through the negatively biased grid.

10. 10. The method of claim 9, further comprising etching away redeposited material from the grid.

11. 10. The method of claim 9, wherein directing an ion beam through the negatively biased grid comprises directing a wide, defocused ion beam.

12. The method according to any one of claims 9 to 11, wherein the grid is the most downstream grid.

13. The method of any one of claims 9 to 11, wherein applying a negative bias comprises applying a negative voltage of between 50V and 800V for at least 30 seconds.

14. 14. The method of claim 13, wherein applying a negative voltage is performed for a maximum of 180 minutes.

15. 1. A method for disposing a plurality of grids in an ion beam system, the plurality of grids having a plurality of holes therethrough and disposed between an ion beam source and a target, comprising: applying a negative bias to a grid in the ion beam system that is furthest downstream from the target; directing an ion beam through the negatively biased grid to condition the negatively biased grid and form a hexagonal pattern on a surface of the conditioned negatively biased grid; determining whether centers of the holes in the conditioned negatively biased grid are aligned with centers of hexagons of the hexagonal pattern.

16. 16. The method of claim 15, further comprising: adjusting a position of at least one of the plurality of grids in response to determining that the plurality of centers of the plurality of holes are not aligned with the plurality of centers of the plurality of hexagons.

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