Ion source and metals used in making components thereof and method of making same

Abstract

An ion source is capable of generating and/or emitting an ion beam which may be used to deposit a layer on a substrate or to perform other functions. In certain example embodiments, techniques for reducing the costs associated with producing ion sources and/or elements thereof are provided. Such techniques may include, for example, forming the inner and/or outer cathode(s) from 1018 mild steel and/or segmented pieces. Such techniques also or instead include, for example, forming the ion source body from a single steel U-channel, or from segmented pieces making up the same. These techniques may be used alone or in various combinations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages will be better and more completely understood by reference to the following detailed description of exemplary illustrative embodiments in conjunction with the drawings, of which:

FIG. 1 is a schematic partial cross-sectional view of a conventional ion source;

FIG. 2 is a sectional view taken along section line II-II of FIG. 1;

FIG. 3 is a sectional view similar to FIG. 2, taken along section line II-II in FIG. 1, in another embodiment illustrating that the ion source may be shaped in an oval manner instead of in a circular manner;

FIG. 4 is an exploded top view of sample pieces from which the outer cathode may be machined in accordance with an example embodiment of this invention;

FIG. 5 is a top view of the sample pieces from FIG. 4 having been assembled in accordance with an example embodiment of this invention;

FIG. 6 is a sectional view taken along the section line 6-6 of FIG. 5; and,

FIG. 7 is a view of a sample segmented outer cathode in accordance with an example embodiment of this invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

In the following descriptions, example embodiments will be described as relating to different types of steels and/or segmented designs for both the inner and/or outer cathode, and/or the ion source body. However, it will be appreciated that the example embodiments herein relate to various combinations thereof, and that the present invention is not limited to any specific combination. Thus, according to certain example embodiments, the type of steel for the inner and/or outer cathode may be chosen independent of the design of the inner and/or outer cathode. Similarly, according to certain example embodiments, the type of steel for the ion source may be chosen independent of the design of the ion source. Finally, the type of steel for and design of the inner and/or outer cathode may be chosen independent of the type of steel for and design of the ion source body. Different inventions herein may or may not be used in combination with each other. The ion source may be of the cold cathode closed-drift type in certain example embodiments of this invention.

Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views.

1. Example Embodiments Relating to the Inner and/or Outer Cathode

1.1 Choice of Metal

It will be appreciated that the example embodiments described below may relate to the use of steel and/or annealing of either the inner cathode, the outer cathode, or both.

As noted above, 1008 mild steel conventionally has been used for inner and/or outer cathodes (e.g., see the cathode at reference numerals 5, 7 and 11 in FIGS. 1-3). This is because 1008 steel generally has advantageous magnetic properties. In particular, one reason 1008 steel has been preferred relates to the lower percentage of carbon—specifically, as specified by the AISI, 1008 steel has only about 0.1% carbon (whereas 1018 steel has about 0.14-0.2% carbon). Yet, as noted above, 1008 steel is hard to machine and generally is more expensive because it is less readily available. Thus, it would be advantageous to provide an inner and/or outer cathode in an ion source that has substantially similar magnetic properties to, but is less costly and easier to machine than, an inner and/or outer cathode formed from 1008 steel.

It has been determined that annealed 1018 mild steel (e.g. AISI standard hot-rolled 1018 steel) is surprisingly advantageous compared to 1008 mild steel, when used to form the inner and/or outer cathode 5, 7 and/or 11 of an ion source. 1018 grade steel has been found to be easier to machine than 1008 steel. Using 1018 mild steel may also reduce the costs associated with manufacturing inner and/or outer cathodes for ion sources because of the availability of 1018 steel. Additionally, the annealing process may make the steel yet more malleable and ductile, thus making it easier to machine and potentially reducing the machining-related costs in making ion sources.

The annealing process also may reduce defects in the lattice structure of the steel. Thus, the 1018 steel may perform similar to 1008 mild steel with respect to its magnetic properties. For example, after the 1018 steel is annealed, the associated Brinell hardness (500 HBW) may drop from about 143 HB to about 85 HB, thus making it more malleable and ductile. However, it will be appreciated that as the 1018 steel is annealed, the associated Brinell hardness (500 HBW) may drop from about 110-150 HB to about 80-105 HB, thus making it more malleable and ductile. Defects in the lattice structure also may be reduced. Moreover, after machining, it is possible that the 1018 could be rehardened by water quenching and/or brine quenching, or the like. Also, the magnetic flux density (B) vs. magnetic field strength (H) hysteresis loops for the 1008 steel and annealed 1018 steel may compare fairly well with each other. Annealing is preferred in certain example non-limiting instances, as the B vs. H hysteresis loops for 1008 steel and non-annealed 1018 compare fairly well with each other. A full anneal may be achieved in certain example instances, for example, by soaking the 1018 steel at about 890° C., followed by furnace cooling.

It will be appreciated that the substitution of steels and/or annealing has very slight, if any, effect on the electrical properties of the inner and/or outer cathode(s) of the ion source. It will be appreciated that such techniques may also or instead be used for an anode 25, in addition to or apart from changes to the inner and/or outer cathode. Additionally, where the cathode 5, 7, 11 and anode 25 are reversed, the techniques similarly may apply to inner and/or outer anodes.

1.2 Segmented Design

As noted above, machining the outer cathode may be difficult and costly because of, for example, its complexity, the high cost of the materials, etc. However, it has been determined that a segmented design for the outer cathode 5, 7 may reduce the costs and difficulties associated with constructing an outer cathode. Costs may be reduced yet further by using a mild steel (e.g. 1018 steel) with a segmented design in certain optional instances.

An example segmented design using four pieces will now be described with reference to FIGS. 4-7. Although, certain example embodiments are described as having four pieces, the invention is not so limited. For example, more or fewer pieces may be used for the outer cathode according to the techniques set forth herein. However, it has been determined that forming an outer cathode from four pieces is advantageous because such example embodiments are easy to machine and assemble at reduced costs.

FIG. 4 is an exploded view of sample pieces from which the outer cathode 5 may be machined in accordance with an example embodiment of this invention. FIG. 4 shows top and bottom pieces 40a-b and left and right pieces 42a-b (as viewed from above for example). Top and bottom pieces 40a-b at least initially are substantially rectangular shaped, and left and right pieces 42a-b at least initially are substantially U-shaped. However, it will be appreciated that other shapes may instead be used. For example, left and right pieces 42a-b may be substantially square shaped or tapered in shape, and/or the center portions may be removed to produce substantially concave left and/or right pieces. Care may be taken when selecting the pieces from which the segments of the outer cathode are to be formed, so as to reduce the amount of wasted material. Also, it will be appreciated that other shapes of the pieces may be used based on the ultimate shape of outer cathode desired (e.g. differently sized and/or shaped pieces may be used for substantially circular outer cathodes).

Top and bottom pieces 40a-b and left and right pieces 42a-b (again, top, bottom, left and right are used as viewed from above as in FIGS. 4-5) may have complementary notches to facilitate the connections therebetween in certain example embodiments of this invention. For example, top piece 40a may have slanting notches 44a-b, to engage with slanting notches 46a-b on left and right pieces 42a-b, respectively. Similarly, bottom piece 40b may have slanting notches 44c-d, to engage with slanting notches 46c-d on left and right pieces 42a-b, respectively. It will be appreciated that the sizes and shapes of the notches are shown by way of example and without limitation. For example, in other example embodiments of this invention, facilitation of the connection between the pieces may instead be made with, for example, tongue-and-groove type connections, o-ring connections, adhesives, or the like.

FIG. 5 is a top view of the sample pieces from FIG. 4 having been assembled in accordance with an example embodiment of this invention. The dashed line in FIG. 5 indicates the portion of the assembly from which the outer cathode 5 ultimately will be formed. In particular, the assembled outer cathode will comprise four pieces according to this example embodiment—namely, top and bottom pieces 50a-b, and left and right pieces 52a-b. The assembly will be substantially racetrack shaped according to this example embodiment, though the invention is not so limited.

FIG. 6 is a side cross-sectional view taken along the section line 6-6 of FIG. 5. The top and bottom portions 50a-b are shown in FIG. 6 as slanting inward. However, it will be appreciated that this particular feature of the cathode is provided by way of example and without limitation.

FIG. 7 is a view of a sample segmented outer cathode 70 in accordance with an example embodiment, shown as comprising top and bottom pieces 50a-b, and left and right pieces 52a-b. The pieces may be bolted to the outer housing (e.g. using bolts 64a-b as shown in FIG. 6, or any other suitable structure) and may thereby come together to form the substantially racetrack-shaped outer cathode. According to certain example embodiments, the pieces will come together with a tolerance of about less than about 0.001″ clearance. It will be appreciated that if the gap between the pieces is too large, then the electrical field will be adversely affected (e.g. it may break down).

It will be appreciated that the pieces may be held together in other ways apart from, or in addition to, the bolts. For example, the pieces may be adhered to one another and/or to the outer housing using an adhesive.

It will be appreciated that such techniques may be used for an anode 25, in addition to or apart from changes to the outer cathode. Additionally, where the cathode and anode are reversed, the techniques similarly may apply to the outer anode.

2. Example Embodiments Related to Ion Source Bodies

2.1 Standard U-Channel Steel

An ion source body may be manufactured using a rectified piece of a standard construction steel U-channel in certain example embodiments of this invention (instead of a standard block-shaped cast of steel). Manufacturing the source body from a standard construction steel U-channel may substantially reduce machining costs due to less material being wasted and easier machining processes, thereby resulting in an overall cost reduction. In certain example embodiments, stock U-channels may be used. However, it will be appreciated that some machining may be necessary, such as crimping or bending the ends of the Us to form the inwardly protruding portions of the outer cathode 5. Thus, ion source bodies may be produced without having to (or with a reduced need to) machine a solid piece of steel.

2.2 Standard U-Channel Steel with Segmented Design

Certain example embodiments reduce the manufacturing cost of the ion source by replacing the one piece construction body of the ion source with an arrangement of several (e.g., three) plates, thereby forming a U-channel after assembly of the multiple pieces. More simple pieces may be used as compared to a solid piece of steel, and the amount of material wasted also may be reduced. The several steel plates may be attached together, for example, using hardware screws, welds, and/or o-ring seals. In those example embodiments where the several plates are attached together in whole or in part with o-ring seals, it may be necessary to machine the plates to provide o-ring grooves for engaging with the o-rings, thus forming the seal. In those embodiments where hardware screws are used, the screws need not have any special magnetic and/or electrical properties.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An ion source comprising: an anode,an inner cathode and an outer cathode,a discharge gap defined between the inner and outer cathodes;a power supply in electrical communication with one or more of the anode, the inner cathode, and/or the outer cathode;at least one magnet capable of generating a magnetic field proximate to the discharge gap; andwherein the inner cathode and/or the outer cathode comprises annealed 1018 mild steel.

2. The ion source of claim 1, wherein the 1018 mild steel is soaked at high temperature and cooled so as to be annealed.

3. The ion source of claim 1, wherein at least the inner cathode is made of annealed 1018 steel.

4. The ion source of claim 1, wherein at least the outer cathode is made of annealed 1018 steel.

5. An ion source comprising: an anode,a cathode,a discharge gap defined proximate the anode and cathode;a power supply in electrical communication with the anode and/or cathode;at least one magnet capable of generating a magnetic field proximate the discharge gap; andwherein the anode and/or cathode comprises 1018 mild steel.

6. The ion source of claim 5, wherein at least part of the cathode comprises annealed 1018 mild steel.

7. An ion source comprising: an anode,an inner cathode and an outer cathode,a discharge gap defined between the inner and outer cathodes;a power supply in electrical communication with one or more of the anode, the inner cathode, and/or the outer cathode;at least one magnet capable of generating a magnetic field proximate to the discharge gap; andwherein the outer cathode is segmented and comprises, when viewed from above: first and second spaced apart substantially rectangular portions, and first and second substantially U-shaped portions positioned between at least the first and second substantially rectangular portions.

8. The ion source of claim 7, wherein notches disposed at each end of each of the substantially rectangular portions engage notches defined in the substantially U-shaped portions so as to permit the substantially rectangular portions to fittingly engage the substantially U-shaped portions.

9. The ion source of claim 7, wherein the first and second spaced apart substantially rectangular portions, and the first and second substantially U-shaped portions, each comprise 1018 mild steel.

10. A method of making an ion source, the method comprising: providing an anode,providing a plurality of pieces comprising steel for an outer cathode, and attaching the plurality of pieces comprising steel together to form the outer cathode;providing an inner cathode;assembling the anode, inner cathode and outer cathode in an ion source apparatus so as to form a discharge gap of the ion source defined between the inner and outer cathodes.

11. The method of claim 10, wherein the plurality of pieces comprising steel for the outer cathode include, in the outer cathode as assembled, first and second spaced apart substantially rectangular portions, and first and second substantially U-shaped portions positioned between at least the first and second substantially rectangular portions.

12. The method of claim 11, wherein the first and second spaced apart substantially rectangular portions, and the first and second substantially U-shaped portions, each comprise 1018 mild steel.

13. A method of making an ion source, the method comprising: providing an anode,providing a steel U-channel;processing the U-channel to form at least an outer cathode for the ion source; andassembling the anode, an inner cathode and the outer cathode formed using the U-channel in an ion source apparatus so as to form a discharge gap of the ion source defined between the inner and outer cathodes.

14. The method of claim 13, wherein said processing of the U-channel comprises bending respective top ends of the U of the U-channel inwardly to form discharge gap defining portions of the outer cathode.