Patent Publication Number: US-RE38358-E

Title: Cold cathode ion beam deposition apparatus with segregated gas flow

Description:
This invention relates to a cold cathode ion beam deposition apparatus with segregated gas flow, and corresponding method. More particularly, this invention relates to a cold cathode ion beam deposition apparatus wherein different gases are caused to flow through different flow channels toward an area of energetic electrons in order to provide a more efficient ion beam deposition apparatus and corresponding method. 
     BACKGROUND OF THE INVENTION 
     An ion source is a device that causes gas molecules to be ionized and then focuses, accelerates, and emits the ionized gas molecules and/or atoms in a beam toward a substrate. Such an ion beam may be used for various technical and technological purposes, including but not limited to, cleaning, activation, polishing, etching, and/or deposition of thin film coatings. Exemplary ion sources are disclosed, for example, in U.S. Pat. Nos. 6,037,717; 6,002,208; and 5,656,819, the disclosures of which are all hereby incorporated herein by reference. 
     FIGS. 1 and 2 illustrate a conventional ion source. In particular, FIG. 1 is a side cross-sectional view of an ion beam source with a circular ion beam emitting slit, and FIG. 2 is a corresponding sectional plan view along section line II—II of FIG.  1 . 
     FIG. 3 is a sectional plan view similar to FIG. 2, for purposes of illustrating that the FIG. 1 ion beam source may have an oval ion beam emitting slit as opposed to a circular ion beam emitting slit. 
     Referring to FIGS. 1-3, the ion source includes hollow housing  3  made of a magnetoconductive material such as mild steel, which is used as a cathode  5 . Cathode  5  includes cylindrical or oval side wall  7 , a closed or partially closed bottom wall  9 , and an approximately flat top wall  11  in which a circular or oval ion emitting slit  15  is defined. Ion emitting slit  15  includes an inner periphery  17  as well as an outer periphery  19 . 
     Working gas supply aperture or hole  21  is formed in bottom wall  9 . Flat top wall  11  functions as an accelerating electrode. A magnetic system in the form of a cylindrical permanent magnet  23  with poles N and S of opposite polarity is placed inside housing  3  between bottom wall  9  and top wall  11 . The N-pole faces flat top wall  11 , while the S-pole faces bottom wall  9  of the ion source. The purpose of the magnetic system, including magnet  23  with a closed magnetic circuit formed by the magnet  23 , cathode  5 , side wall(s)  7 , and bottom wall  9 , is to induce a substantially transverse magnetic field (MF) in an area proximate ion emitting slit  15 . 
     A circular or oval shaped anode  25 , electrically connected to positive pole  27  of electric power source  29 , is arranged in the interior of housing  3  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 ring  31  (e.g., of ceramic). Anode  25  defines a central opening  33  therein in which magnet  23  is located. Negative pole  35  of electric power source  29  is connected to housing  3  (and thus to cathode  5 ) generally at  37 , so that the cathode and housing are grounded (GR). 
     Located above housing  3  (and thus above cathode  5 ) of the ion source of FIGS. 1-3 is vacuum chamber  41 . Chamber  41  includes evacuation port  43  that is connected to a source of vacuum (not shown). An object or substrate  45  to be treated (e.g., coated, etched, cleaned, etc.) is supported within vacuum chamber  41  above ion emitting slit  15  (e.g., by gluing it, fastening it, or otherwise supporting it on an insulator block  47 ). Thus, substrate  45  can remain electrically and magnetically isolated from the housing of vacuum chamber  41 , yet electrically connected via line  49  to negative pole  35  of power source  29 . Since the interior of housing  3  can communicate with the interior of vacuum chamber  41 , all lines that electrically connect power source  29  with anode  25  and substrate  45  may pass into the interior of housing  3  and/or chamber  41  via conventional electrically feed through devices  51 . 
     The conventional ion beam source of FIGS. 1-3 is intended for the formation of a unilaterally directed tubular ion beam  53 , flowing in the direction of arrow  55  toward a surface of substrate  45 . Ion beam  53  emitted from the area of slit  15  is in the form of a circle in the FIG. 2 embodiment and in the form of an oval (i.e., race track) in the FIG. 3 embodiment. 
     The ion beam source of FIGS. 1-3 operates as follows. Vacuum chamber  41  is evacuated, and a working gas  57  is fed into the interior of housing  3  via aperture  21 . Power supply  29  is activated and an electric field is generated between anode  25  and cathode  5 , which accelerates electrons  59  to high energy. Electron collisions with the working gas in or proximate gap or slit  15  leads to ionization and a plasma is generated “Plasma” herein means a cloud of gas including ions of a material to be accelerated toward substrate  45 . The plasma expands and fills a region including slit  15 . An electric field is produced in slit  15 , oriented in the direction of arrow  55  (substantially perpendicular to the transverse magnetic field) which causes ions to propagate toward substrate  45 . Electrons in the ion acceleration space in slit  15  are propelled by the known E x B drift in a closed loop path within the region of crossed electric and magnetic field lines proximate slit  15 . These circulating electrons contribute to ionization of the working gas, so that the zone of ionizing collisions extends beyond the electrical gap  63  between the anode and cathode and includes the region proximate slit  15 . 
     For purposes of example, consider the situation where a silane gas  57  is utilized by the ion source of FIGS. 1-3. The silane gas, including the silane inclusive molecules therein, passes through the gap at  63  between anode  25  and cathode  5 . Unfortunately, certain of the elements in silane gas are insulative in nature (e.g., silicon carbide may be an insulator in certain applications). Insulating deposits (e.g., silicon carbide) can quickly build up on the respective surfaces of anode  25  and/or cathode  5  proximate gap  63 . This can interfere with gas flow through the gap or slit, or alternatively it can adversely affect the electric field potential between the anode and cathode proximate slit  15 . In either case, operability and/or efficiency of the ion beam source is adversely affected. In sum, the flow of gas which produces a substantial amount of insulative material buildup in electrical gap  63  on the anode and cathode may be undesirable in certain applications. 
     Moreover, electrical performance of the ion source is sensitive to parameters of gases within gap  63  (i.e., the electrical gap between the anode  25  and cathode  5 ). For example, electrical performance of the source is sensitive to characteristics such as the density of the gas within gap  63 , the residence time of the gas within gap  63 , and/or the molecular weight of the gas within gap  63 . Changes in gas chemistry at gap  63  (intentional or unintentional) can alter the characteristics of ion beam  53  (e.g., with regard to energy and/or current density). This problem is particularly troublesome at high total flow conditions where the beam  53  can undergo a significant discontinuous transition between two operational modes (e.g., high energy/low current and low energy/high current). 
     U.S. Pat. Nos. 5,508,368; 5,888,593: and 5,973,447 relate to ion sources, each of these patents being hereby incorporated herein by reference. Unfortunately, the sources of the &#39;368, &#39;593 and &#39;447 patents primarily relate to thermionic emissive (hot) electron cathodes. This is undesirable, as cold-cathode sources such as that of the instant invention typically operate at higher voltages and/or lower gas flows. These advantages of cold-cathode sources translate into the ability to deposit much harder materials more efficiently (e.g., ta-C versus conventional DLC), and/or the need for fewer or less powerful pump(s). Additional problems with conventional ion sources are discussed in U.S. Pat. No. 6,002,208, in the context of the known Kaufman-type source (e.g., see col. 1 of the &#39;208 patent where it is indicated that such sources are disadvantageous in that they are not suitable for treating large surfaces and/or have low intensity). 
     In view of the above, it will be apparent to those skilled in the an that there exists a need for an ion source including a more efficient gas flow design. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a cold cathode closed drift ion source including a segregated gas flow system. 
     Another object of this invention is to provide a cold cathode ion source in which a one gas is caused to flow through the electrical gap between the anode and cathode toward an ion emitting slit, and another gas is caused to flow toward the slit but without much of said another gas passing through the electrical gap between the anode and cathode (i.e., preferably less than 50% of said another gas passes through this electrical gap, more preferably less than about 30%, and most preferably less than about 20%). 
     Another object of this invention is to provide a segregated gas flow arrangement in the context of a cold cathode ion source in order to reduce the likelihood of undesired insulative material buildups in the electrical gap between the anode and cathode. 
     Yet another object of this invention is to provide an ion source including a first gas flow path and a second gas flow path; wherein the first gas flow path accommodates the flow of a first gas toward the ion emitting slit and the second path accommodates the flow of a second gas (different from the first gas) toward the ion emitting slit. 
     Another object of this invention is to fulfill any and/or all of the aforesaid objects and/or needs. 
     Generally speaking, this invention fulfills any one or more of the aforesaid needs and/or objects by providing an ion beam source capable of emitting an ion beam toward a substrate, the ion beam source comprising: 
     a cathode; 
     an anode located at least partially between respective portions of said cathode, said anode including an inner periphery and an outer periphery; 
     an electrical gap defined between said anode and said cathode; 
     a magnet for generating a magnetic field proximate an ion emitting aperture defined in said cathode, wherein an ion beam is emitted toward a substrate from an area in or proximate said ion emitting aperture; 
     at least one first gas flow aperture or channel for enabling a first gas to flow around a periphery of the anode and through said electrical gap toward said ion emitting aperture; and 
     al least one second gas flow channel or aperture located within a body of said anode between inner and outer peripheries of said anode; said second gas flow channel or aperture for enabling a second gas to flow through said second gas flow channel or aperture toward said ion emitting aperture. 
     This invention further fulfills any one or more of the aforesaid needs and/or objects by providing An ion beam source capable of emitting an ion beam toward a substrate, the ion beam source comprising: 
     an anode and a cathode, with an electrical gap defined between said anode and said cathode; 
     at least one first gas flow aperture or channel for enabling a first gas to flow through said electrical gap toward an aperture or slit in said cathode; and 
     at least one second gas flow channel or aperture for enabling a second gas to flow through said second gas flow channel or aperture toward said aperture or slit without much of the second gas having to flow through said electrical gap. 
     Certain embodiments of this invention still further fulfill one or more of the aforesaid needs and/or objects by providing a method of emitting an ion beam toward a substrate, the method comprising the steps of: 
     providing an ion beam source including an anode and a cathode, so that an electrical gap is provided between the anode and cathode; 
     causing a first gas to flow through a first flow area around a periphery of the anode and through the electrical gap toward an aperture or slit defined in the cathode; 
     causing a second gas to flow through a second gas flow channel or aperture defined in a body of the anode and toward the aperture or slit in the cathode: and 
     ionizing at least a portion of at least one of the fast and second gases proximate the aperture or slit in the cathode and causing an ion beam to be directed from the aperture or slit in the cathode toward the substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic partial cross-sectional view of a conventional cold cathode closed drift ion source. 
     FIG. 2 is a sectional view taking along section line II of FIG.  1 . 
     FIG. 3 is a sectional view similar to that of FIG. 2 along section line  11 , illustrating that the ion source of FIG. 1 may be shaped in an oval manner as opposed to a cylindrical or circular manner. 
     FIG. 4 is a schematic and partial sectional view of a cold cathode closed drift ion source with segregated gas flow according to an embodiment of this invention. 
     FIG. 5 is a schematic and partial sectional view of certain portions of the ion source of FIG.  4 . 
     FIG. 6 is a schematic and partial sectional view of a cold cathode closed drift ion source with segregated gas flow according to another embodiment of this invention. 
     FIG. 7 is a top view of the anode and magnet of the FIG. 4-5 embodiment of this invention. 
     FIG. 8 is a op view of the anode and magnet of another embodiment of this invention, illustrating that a plurality of different flow passages may to provided within the body of the anode. 
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THIS INVENTION 
     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 the present invention with unnecessary detail. Referring now more particularly to the accompanying drawings, in which like reference numerals indicate like parts/elements/components/areas throughout the several views. 
     FIG. 4 is a schematic and partial sectional view of an ion source according to an exemplary embodiment of this invention. The cold cathode closed drift type ion source of FIG. 4 is similar in many respects to that of FIGS. 1-3. Closed loop ion emitting slit  15  may be circular, cylindrical, rectangular, triangular, elliptical, or oval in shape according to different embodiments of this invention. Shapes herein are for purposes of example only, and are not intended to be limiting. 
     The terms “aperture”, “channel” and “slit” are used herein for purposes of convenience are not intended to be limited as to shape or size. For example, an aperture herein may be of any shape or size (e.g., circular, rectangular, triangular, semi-circular, trapezoidal, channel-shaped, slit-shaped, or the like). Thus, a “slit”may be both a slit as well as an aperture herein, as may a channel. Likewise, the term “aperture” as used herein includes simple holes as well as apertures in the form of slit, channels, and the like. 
     The cold cathode closed drift ion source of FIG. 4 may be utilized in order to ionize gas molecules and then focus them and cause them to be accelerated and emitted as a beam  53  toward a substrate  45 . This ion beam may be utilized for various technical and technological purposes, including but not limited to, cleaning the substrate, activating something on the substrate, polishing the substrate, etching a portion of the substrate, and/or depositing a thin film coating(s) and/or layer(s) on the substrate. 
     Anode  25  includes a body or main body defining an inner periphery  15   a  and an outer periphery  15   b . Thus, within the main body of the anode  25  is an aperture in which magnet  23  is located. The body of anode  25  includes gas inlet aperture  71  defined therein. The inner and outer peripheries of the anode  25  may be circular, oval, elliptical, triangular, rectangular, or otherwise shaped in different embodiments of this invention. The inner and outer peripheries of the anode  25  may be concentric in certain embodiments, and non-concentric in other embodiments of this invention. 
     Referring to FIGS. 4-5 and  7 , in certain exemplary embodiments of this invention anode  25  is at a positive potential and cathode  5  is either at a grounded or negative potential. This causes active electrons to pass through electrical gap  63  between anode  25  and cathode  5 . Magnetic field (MF) caused at least in part by magnet  23  proximate slit  15  tends to keep the active electrons proximate the slit so that they can ionize gas in the vicinity of the slit. Gas molecules and/or atoms flowing proximate slit  15  (some of which may flow through electric gap  63 ) are thus bombarded by electrons  59  and ionized in a known manner. Because of at least the potential of anode  25 , the ions are propelled (i.e., accelerated) outwardly from slit  15  in the form of a beam  53  toward substrate  45 . Substrate  45  may be grounded as shown in FIG. 4 according to certain embodiments of this invention. In other embodiments of this invention, substrate  45  need not be grounded. 
     The particular magnetic circuit illustrated in the drawings is for purposes of example only, and clearly is not intended to be limiting. The magnet may be positioned as illustrated within the circumference of anode  25 , or instead it may be provided at other locations in order to produce the transverse magnetic field in slit  15 . In other words, there are many different ways of producing the transverse field in slit  15 . For example, as an alternative to the illustrated embodiments, cylindrical magnets could be embedded in the outer cylindrical housing with all or most of the cylindrical magnets having polarities oriented in approximately the same direction and aligned along the axis of the ion source. Then, the central magnet could be replaced with magneto-conductive material, and a closed circuit (with no or minimal gaps) that connects to both surfaces defining slit  25  is till obtained. 
     In accordance with different embodiments of this invention, different gases are caused to flow toward slit  15  by way of different flow paths. This is done in order to reduce the likelihood of insulative material buildup in electric gap  63  and/or to render the ion source more efficient in nature. 
     Referring to FIGS. 4-5, it is possible to utilize two, three or more different types of gas in the source according to different embodiments of this invention. These gases include maintenance gas, chemically reactive gas, and/or depositing gas, or any combination thereof. 
     In general, depositing gas (e.g., silane, siloxane, acetylene, etc.) is utilized whenever it is desired to deposit a thin film coating or layer(s) on surface  46  of substrate  45  where the coating is to include material from the depositing gas. In such a case, molecules of the depositing gas are ionized proximate slit  15  by the active electrons which are contained throughout much of the magnetic field (MF). These ions from the depositing gas are then accelerated outwardly as at least part of beam  53  toward the substrate and are deposited on surface  46  thereof. In such a manner, thin films may be deposited on substrate  45 , such as diamond-like carbon (DLC) thin films, and the like. Exemplary depositing gases (e.g., C 2 H 2  and/or TMS) which may be used to deposit DLC and other materials on a substrate are disclosed along with the resulting thin film coatings in U.S. Ser. Nos. 09/303,548, filed May 3, 1999, and 09/442,805, filed Nov. 18, 1999, the disclosures of which are both hereby incorporated herein by reference. 
     As illustrated in FIG. 5, depositing gas may flow toward slit  15  through flow path or aperture  71  defined in an otherwise solid portion of the body of anode  25 . The location of gas flow aperture or path  71  immediately beneath slit  15  enables the depositing gas (which often includes insulative components such as silicon (Si)) to flow directly into slit  15  without much of the gas having to pass through the electrical gap  63  between anode  25  and cathode  5 . Thus, in certain embodiments of this invention, preferably less than 50% of the depositing gas passes through electrical gap  63 , more preferably less than about 30%, and most preferably less than about 20%). By reducing the amount of depositing gas (e.g., a hydrocarbon or organosilicon gas that results in buildup of insulative material in the electrical gap  63 ) that flows through the electrical gap  63  between the anode and cathode, the tendency of insulative material(s) from the depositing gas to build up on the anode and/or cathode in the area of electric gap  63  is reduced. Thus, electrical characteristics of gap  63  can be maintained in a more efficient and easy manner. 
     Once the molecules of the depositing gas have flowed through flow channel or aperture  71  in anode  25  and reached the MF area proximate slit  15 , they are bombarded by active electrons located in the MF proximate the slit and ionized so that they are expelled as at least pact of ion beam  53  toward substrate  45  (e.g., so that a thin film coating(s) can be deposited on the substrate; where the chemical make-up of such a coating(s) depends on the type of gas(es) used). 
     Maintenance gas (e.g., argon, krypton or xenon) may be utilized in combination with depositing gas in certain embodiments of this invention. However, as illustrated in FIGS. 4 and 5, all of the maintenance gas need not flow through the same channel or aperture  71  as the depositing gas. Instead, much of the maintenance gas (e.g., all of the maintenance gas in certain embodiments; or even only a portion of maintenance gas in other embodiments) flows around the inner and/or outer periphery(ies)  15   a  and/or  15   b  of the anode  25  and through one or more of the respective electrical gap(s)  63  between the anode  25  and cathode  5 , before reaching slit  15 . As shown in FIGS. 4-5, maintenance gas may flow through one or both of respective channels or flow paths  73 ,  75  around the inner and/or outer periphery (ies) of anode  25 . The provision of this maintenance gas in the electric gap  63  between the anode and cathode defines much of the electrical performance of the ion source (i.e., the maintenance gas is the fuel which runs the plasma generated in the vicinity of the slit). For example, the flow rate of the maintenance gas within electric gap(s)  63  determines certain electrical characteristics, e.g., voltage and/or current between the anode/cathode. Depending upon the plasma in the gap(s)  63 , the current in the gap is translated into a beam current, i.e., a flux of ions expelled outwardly in beam  53  toward the substrate. The higher the current in the gap, the greater the ion flux. Thus, it is important to control the amount of gas in respective electric gap(s)  63 . As discussed above, control of the amounts of gas in gaps  63  may be achieved in part by reducing the likelihood of the buildup of insulative material in gaps  63  which may reduce the flow of maintenance gas therethrough. Moreover, it will be appreciated by those skilled in the an that the depositing gas may be changed without having to change the maintenance gas in certain embodiments of this invention, so that the type of coating/layer being deposited on substrate can be changed without having to change significant electrical characteristics of the beam and/or gap. 
     Accordingly, it can be seen that in many embodiments it may be desirable to utilize a first gas as a depositing gas(es) (e.g., silane, siloxane, silazane, cyclohexane, acetylene, etc.) which produces substantial insulative deposits (e.g., SiC); and a second gas(es) (e.g., argon, xenon, krypton, etc.) as a maintenance gas which will not typically cause much material buildup on the anode or cathode in gap(s)  63 . Thus, the non-insulative maintenance gas passed through one or more of channels or paths  73 ,  75  may be utilized to control and/or determine the electrical characteristics of ion beam  53 , while the depositing gas injected through flow path or aperture  71  within the anode itself may be utilized to determine which ions are to be expelled in beam  53  for deposition on the surface of substrate  45  (it is noted that in certain embodiments of this invention all maintenance gas flows through channels  73  and/or  75  and none through channel  71 ; while in other embodiments of this invention dome maintenance gas may flow through  71  and/or a portion of depositing gas may flow through channel(s)  73 ,  75  in addition to channel  71 ). Thus, in certain embodiments of this invention the depositing gas may be changed and/or adjusted with relative frequency, without having to worry about adversely affecting or undesirably changing the electrical characteristics (e.g., ion energy) of the beam  53 . 
     In short, by injecting the depositing gas through a central portion the body of anode  25  (i.e., between the inner and outer peripheries  15   a  and  156 , respectively, of the anode) beneath slit  15  so that much of the depositing gas does not have to pass through the direct electrical gap(s)  63  between the anode and cathode, less insulative material deposition on the anode and/or cathode occurs in gap(s)  63 . Moreover, when it is desired to change the material for a coating and/or layer being deposited on substrate  45 , the depositing gas can be changed without unduly altering the electrical characteristics of the ion beam  53  (because the maintenance gas need not be changed). Thus, changes in beam  53  chemistry can be achieved without unduly altering the characteristics of the beam itself. 
     The reduction of insulative material buildup in gaps  63  is of particular importance when producing insulating coatings, such as silicon inclusive diamond-like carbon layers/coatings which are highly electrically insulating. Such insulative deposits on the anode and/or cathode in gap(s)  63  can disrupt and/or terminate the inter-electrode plasma (the plasma which generates the beam ions) between the anode and cathode. 
     As discussed above, the ion source of FIGS. 4-5 and  7  may be utilized for purposes other than deposition of coatings and/or layers on substrate  45 . For example, the ion source of FIGS. 4-5 and  7  may be utilized to direct an ion beam  53  toward substrate  45  in order to etch a portion of the substrate (e.g., glass or plastic substrate), or alternatively may be used to clean a surface of the substrate. 
     In exemplary etching embodiments of this invention, a chemically reactive gas may be utilized and injected through flow path  71  instead of the aforesaid depositing gas. For example, if it is desired to use the ion source to etch a substrate  45  of plastic material, a maintenance gas of argon may be used in combination with a reactive gas of oxygen. The oxygen would be passed through flow channel  71  in the body of the anode (surrounding the magnet), while the argon would be injected through one or both of flow paths  73 ,  75  around the inner and outer peripheries of the anode  25 . Thus, the oxygen and argon ions mix in the area of slit  15 , but many of the oxygen ions which were injected through aperture  71  would not have passed through electric gap(s)  63 . The mixture of oxygen and argon are ionized by electrons in the MF, and these ions are expelled toward the plastic substrate in beam  53 . The oxygen ions of the beam react with the plastic surface of the substrate in order to etch the same. In other embodiments where it is desired to etch the surface of a substrate  45  of glass, argon maintenance gas may be utilized in combination with CF 4  and/or O 2 reactive gases. In other words, either a depositing gas or a non-depositing reactive gas may be injected through aperture  71  directly into slit  15  (in combination with maintenance gases) in different embodiments of this invention. 
     As shown in FIG. 5, it is also possible to direct depositing gas at  81  toward the MF proximate slit  15  from a position above top wall  11  of the cathode, such that top wall  11  is located between this optional source(s)  82  and anode  25 . Introducing depositing gas at  81  above the top wall  11  may be used either in combination with injecting depositing gas through aperture  71 , or instead of introducing depositing gas through aperture  71 . In still further embodiments, the depositing gas being introduced at  81  may be used in combination with both a maintenance gas introduced at  73 ,  75  and/or reactive gas introduced through channel  71 . 
     When using source(s)  82 , the depositing gas introduced at  81  is directed toward MF where active electrons are present. These reactive electrons ionize the depositing gas so that the ions thereof may be expelled from the vicinity of slit  15  as at least part of beam  53  toward substrate  45  so that they can be deposited on surface  46 . 
     The embodiment of FIGS. 4-5 and  7  (see especially FIG. 7) illustrates a single gas flow aperture or slit  71  that is provided in the body of the anode around the entire periphery of the magnet  23 . In other words, aperture or slit  71  may be shaped in the form of a racetrack, a circle, an oval, a rectangle, an ellipse, or a triangle surrounding the magnet much like the shape of slit  15  (i.e., aperture/slit  71  is continuous in nature and surrounds the magnet when viewed from above as in FIG.  7 ). However, in other embodiments of this invention, aperture  71  need not be continuous and need not surround the magnet. 
     For example, refer to the embodiment of FIG. 8 where instead of a single continuous aperture  71  surrounding the magnet  23 , a plurality of different and spaced apart gas flow apertures  71  are provided in the body of the anode  25  between the inner and outer anode peripheries. Each of the plurality of different flow apertures  71  in the FIG. S embodiment may be in the shape of a circle as shown, or alternatively may be shaped as rectangles, triangles, short slits, curved slits, ovals, ellipses, or the like. Two, three, four, five, six, seven, eight, nine, ten (as illustrated in FIG:  8 ), eleven, or more such apertures  71  may be provided in the body of the anode  25  for gas flow purposes in different embodiments of this invention. Depositing and/or reactive gas(es) may be passed through one or more of apertures  71  in the same manner as discussed above, toward slit  15  so as to attain advantages discussed herein. 
     FIG. 6 illustrates another embodiment of this invention. In the FIG,  6  embodiment, maintenance gas (as described above) is injected through gas flow paths or channels  85  so that the maintenance gas flows through one or more of channels  73 ,  75  around the inner and outer peripheries of anode  25 , respectively, toward slit  15 . In the FIG. 6 embodiment, there is no aperture or hole in the anode for injecting a depositing and/or reactive gas. Thus, for example, depositing gas may be injected at a location  81  through at least one flow path or channel in the side of vacuum chamber  41  above top cathode wall  11 . The depositing gas is directed toward the magnetic field (MF) proximate slit  15 , so that the depositing gas molecules can be ionized and the resulting ions expelled toward substrate  45  in beam  53 . Again, it is beneficial, especially in the case of depositing gases including insulative materials such as silicon, to introduce the depositing gas at a location such as that in FIG. 6 so that much of the depositing gas does not have to pass through the electric gap(es)  63  between the anode and cathode. This reduces the potential of insulative material buildups on the anode and/or cathode in electric gap(s)  63  as discussed above. 
     Once given the above disclosure, many other features, modifications, and improvements will become apparent to the skilled artisan. Such other features, modifications, and improvements are therefore considered to be a part of this invention, the scope of which is to be determined by the following claims and equivalents thereof.