This invention relates to an ion source having an improved cathode design. In certain example embodiments, the ion source comprises a multi-piece outer cathode.
An ion source is a device that causes gas molecules to be ionized and then accelerates and emits the ionized gas molecules and/or atoms toward a substrate. Such an ion source may be used for various purposes, including but not limited to cleaning a substrate, surface activation, polishing, etching, and/or deposition of thin film coatings/layer(s). Example ion sources are disclosed, for example, in U.S. Pat. Nos. 6,359,388; 6,037,717; 6,002,208; 5,656,819, 6,815,690, Ser. Nos. 10/986,456, and 10/419,990, the disclosures of which are all hereby incorporated herein by reference.
Referring to
Deposition and/or plasma maintenance gas supply aperture or hole(s) 21 is/are formed in bottom wall 9. The flat top wall of the cathode functions as an accelerating electrode. A magnetic system including a cylindrical permanent magnet(s) 23 with poles N and S of opposite polarity is placed inside the housing between bottom wall 9 and top wall 11. The purpose of the magnetic system with a closed magnetic circuit formed by the magnet 23 and cathode 5 is to induce a substantially transverse magnetic field (MF) in an area proximate ion emitting slit 15. The ion source may be entirely or partially within a wall 50. In certain instances, wall 50 may entirely surround the source and substrate 45, while in other instances the wall 50 may only partially surround the ion source and/or substrate.
A circular or oval shaped conductive anode 25, electrically connected to the positive pole of electric power source 29, is arranged so as to at least partially surround magnet 23 and be approximately concentric therewith. Anode 25 may be fixed inside the housing by way of insulative ring 31 (e.g., of ceramic). Anode 25 defines a central opening therein in which magnet 23 is located. The negative pole of electric power source 29 is connected to cathode 5, so that the cathode is negative with respect to the anode (e.g., the cathode may be grounded in certain example non-limiting instances).
Generally speaking, the anode 25 may be biased positive by several hundred to a few thousand volts. Meanwhile, the cathode (inner and/or outer portions thereof) may be held at, or close to, ground potential. This is the during ion source operation.
The conventional ion beam source of
The conventional ion beam source of
For purposes of example, consider the situation where a silane and/or acetylene (C2H2) depositing gas is/are utilized by the ion source of
Unfortunately, ion sources suffer from the problem that during use the electrode(s) (e.g., cathode and/or anode) erode over time. For example, consider a situation where the cathode (or anode) is made of steel—which includes iron. During use of the ion source, exposed surface portions of at least the cathode are prone to erosion. This type of electrode erosion is problematic for a number of reasons. First, significant erosion of the cathode over time can cause the width of the slit (i.e., the magnetic gap) to significantly change which in turn can adversely affect ion beam processing conditions and lead to non-uniform coatings, etchings, etc. When enough erosion has occurred to cause the width of the slit/gap to sufficiently change, the electrode(s) have to be replaced with entire new electrode(s).
In view of the above, it will be appreciated that there exists a need in the art for an ion source (and/or corresponding method) that is capable of efficiently dealing with the issue of electrode erosion.
In certain example embodiments of this invention, there is provided an ion source including an anode and a cathode. In certain example embodiments, a multi-piece outer cathode is provided. The multi-piece outer cathode allows precision adjustments to be made, thereby permitting adjustment of the magnetic gap between the inner and outer cathodes. This allows improved performance to be realized, and/or prolonged operating life of certain components. This may also permit multiple types of gap adjustment to be performed with different sized outer cathode end pieces. In certain example embodiments, cathode fabrication costs may also be reduced.
In certain example embodiments of this invention, there is provided an ion source comprising: a conductive cathode comprising an inner cathode and an outer cathode; an ion emitting gap formed at least partially between the inner cathode and the outer cathode; an anode located proximate the ion emitting gap; and wherein the outer cathode comprises a plurality of electrically connected conductive pieces which are at least partially coplanar.
In other example embodiments of this invention, there is provided an ion source comprising: first and second electrodes, wherein the first electrode (e.g., cathode) comprises an inner electrode and an outer electrode that are spaced apart from one another; an ion emitting gap formed at least partially between the inner electrode and the outer electrode; the second electrode (e.g., anode) being located proximate the ion emitting gap; and wherein the outer electrode comprises a plurality of electrically connected conductive pieces which are at least partially coplanar.
a) is a top plan view of a multi-piece outer cathode according to an example embodiment of this invention.
b) is a side plan view of the outer cathode of
c) is a cross sectional view taken along section line C-C′ of
Referring now more particularly to the accompanying drawings, in which like reference numerals indicate like parts throughout the several views (unless otherwise indicated). In this respect, for example, reference numerals used in
In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide an understanding of certain embodiments of the present invention. However, it will apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well known devices, gases, fasteners, and other components/systems are omitted so as to not obscure the description of examples of the present invention with unnecessary detail.
Certain example embodiments of this invention relate to an ion source having a multi-piece outer cathode. The multi-piece outer cathode allows precision adjustments to be made, thereby permitting adjustment of the magnetic gap between the inner and outer cathodes for example. This allows improved performance to be realized, and/or prolonged operating life of certain components. This may also permit multiple types of gap adjustment to be performed with different sized outer cathode pieces. In certain example embodiments, cathode fabrication costs may also be reduced. The ion source in certain example embodiments may be a cold cathode closed drift ion source. Operating pressures may be below atmospheric pressure, and may be similar to those of planar and magnetron sputtering systems.
An ion source using the multi-piece cathode 5b′ of
The ion beam emitted from the ion source may be a diffused beam in certain example embodiments of this invention. However, in other example embodiments, the ion beam from the ion source may be focused or otherwise shaped/oriented.
a) illustrates that the multi-piece outer cathode 5b′ includes four different conductive pieces, namely opposing end pieces 5c and 5d, and opposing side pieces 5e and 5f.
In certain example embodiments of this invention, outer cathode pieces 5c, 5d, 5e and 5f may be made of a conductive material such as stainless steel (e.g., 1012 hot rolled steel, or mild steel), although other materials may also be used. In certain example embodiments, each of the pieces 5c, 5d, 5e and 5f may have a thickness of from about 3-25 mm, more preferably from about 4-15 mm, with an example thickness being about 7 mm. In certain example embodiments, pieces 5c, 5d, 5e and 5f all have substantially the same thickness.
In certain example embodiments, the inner edge/side 6 of each end piece 5c and 5d which helps define the ion emitting slit/gap 15 is arc-shaped, whereas the inner edge/side 8 of each side piece 5e and 5f which helps define the slit/gap 15 is linear-shaped. In certain example embodiments, the side 6 of each end piece 5c and 5d which helps define the ion emitting slit/gap 15 is in the shape of an approximate half-circle. In certain example embodiments, the inner sides/edges 8 of the respective side pieces 5e and 5f are substantially parallel to one another. In certain example embodiments, each end piece (5c, 5d) is located between and directly contacts side pieces 5e, 5f. In certain example embodiments, each side piece (5e, 5f) is located between and directly contacts end pieces 5c, 5d.
As best shown in
The angled portions 71 of the side pieces 5e and 5f abut and/or are adjacent to respective angled portions 75 of the end pieces 5c and 5d (e.g., see
As best shown at the bottom of
Given the multiple pieces 5c, 5d, 5e and 5f making up the outer cathode 5b′, four-way dynamic adjustability of the ion emitting slit/gap 15 can be realized in certain example embodiments of this invention. In particular, given angled portions 71 and 75, each of the pieces 5c, 5d, 5e and 5f can have its position relative to the ion emitting slit/gap 15 adjusted. In other words, each of these pieces can be moved inwardly or outwardly, thereby adjusting the size of the gap. Thus, four-way adjustability can be realized. For example and without limitation, when the anode and cathode wear down (erode) during use of the ion source and the size of the slit/gap 15 between the inner and outer cathodes becomes undesirably large, the end pieces 5c and/or 5d may be replaced with end pieces of a slightly smaller size, while maintaining the side pieces 5e and 5f. After the new end pieces 5c and/or 5d have been inserted (they may have a smaller width than the previous pieces—from top to bottom as viewed in
The multi-piece outer cathode 5b′ discussed above and shown in
In the aforesaid embodiments it is noted that the magnetic stack 23 is illustrated in the center of the source. However, this need not be the case in alternative embodiments, as the central location is used for convenience only and is not a requirement in all instances. It is further noted that the absolute polarity of the magnetic field (North vs. South) is not particularly important to the function of the source. Moreover, it is possible that a ceramic insulator 35 or dark-space gap may be provided between the anode and cathode in certain example instances. In this embodiment or in other embodiments, a gas source 30 may be provided so that gas such as acetylene or the like may be introduced toward the source from the side thereof closest to the substrate 45 (e.g., glass substrate to be milled or coated). Moreover, the positions of the anode and cathode may be switched in certain alternative instances.
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.
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