Abstract:
A low-contaminant dual layer apparatus adapted for use in a flat panel display device is described. The apparatus includes a dual layer electroplated structure for containing the movement of electrons. The electroplated structure resides within an active region of the flat panel display device. The electroplated structure has a cavity adapted to having sub-pixel forming material deposited within and contains substantially no organic material.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This Application is a Continuation-in-Part of commonly-owned Ser. No. 09/310,464 filed May 12, 1999, now U.S. Pat. No. 6,235,179 B1 filed May 12, 1999 and issued May 22, 2001, entitled “ELECTROPLATED STRUCTURE FOR A FLAT PANEL DISPLAY DEVICE” to Besser et al. 
    
    
     FIELD OF THE INVENTION 
     The present claimed invention relates to the field of flat panel displays. More particularly, the present claimed invention relates to interior structures of a flat panel display device. 
     BACKGROUND ART 
     Flat panel display devices often operate using electron emitting structures, such as, for example, Spindt-type field emitters. These types of flat panel displays typically employ a metallized structure to focus or define the path of electrons emitted from the electron emitting structures. In one prior art approach, the structure is referred to as a “focus waffle.” The focus waffle is comprised of a “sheet” or film-like structure having a plurality of openings formed therethrough. The focus waffle is disposed between the electron emitting structures and the faceplate such that emitted electrons pass through openings in the focus waffle structure, and are directed towards corresponding sub-pixel regions. 
     Additionally, the aforementioned sub-pixel regions on the faceplate of flat panel display are typically separated by an opaque mesh-like structure commonly referred to as a black matrix. By separating sub-pixel regions, the black matrix prevents electrons directed at one sub-pixel from being “back-scattered” and striking another sub-pixel. In so doing, the black matrix helps maintain a flat panel display with sharp resolution. In addition, the black matrix is also used as a base on which to locate structures such as, for example, support walls. 
     Unfortunately, due to the extremely high cost of certain types of material used to form the black matrix or focus waffle (especially photo-patternable polyimide material), such prior art black matrix and focus waffle structures are extremely expensive. As a result, a conventional black matrix and/or a focus waffle made of expensive material such as polyimide introduces substantial additional costs to flat panel display fabrication. As yet another disadvantage, such prior art focus waffle and black matrix structures made of organics such as polyimide material are a major source of contamination in flat panel display devices. Typically, such contamination results from electron bombardment of the organic black matrix or focus waffle during normal operation of the flat panel display device. Hence, such “dirty” focus waffle and black matrix structures introduce contaminate particles and/or desorbing gaseous species into the evacuated environment of the flat panel display device. These contaminate particles degrade the performance of the flat panel display device and reduce the effective lifetime of the flat panel display device via contamination of field emission surfaces and other possible mechanisms. 
     Thus, a need exists for a structure on the display cathode which effectively directs electrons emitted from electron emitters. A further need exists on the faceplate for a structure which effectively separates neighboring phosphor sub-pixels. A further need exists for a structure which meets the above-listed needs and which eliminates the use of expensive and contaminant producing material. 
     SUMMARY OF INVENTION 
     The present invention provides, in one embodiment, a structure on the display cathode which effectively directs electrons emitted from electron emitters. The present invention provides, in another embodiment, a structure on the faceplate which effectively separates neighboring phosphor sub-pixels. The present invention, in each of the above-mentioned embodiments, achieves the above-listed accomplishments without requiring the use of expensive and contaminant-producing material such as polyimide. 
     Specifically, in various embodiments, a dual layer electroplated structure for a field emission display device and a method for forming a dual layer electroplated structure for a field emission display device are disclosed. In one embodiment, the present invention is comprised of a method which includes the step of forming an opaque conductive layer over selected portions of a flat panel display device. The present embodiment then electroplates material onto the opaque conductive layer disposed over the selected portions of said flat panel display device. In the present embodiment, these steps are performed such that a dual layer electroplated structure is formed over the selected portions of the flat panel display device. As a result, the present embodiment eliminates the cost and production of outgassed contaminants associated with prior art structures. 
    
    
     These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of this specification, illustrates embodiments of the invention and, together with the description, serve to explain the principles of the invention: 
     FIGS. 1A-1F are side sectional views of process steps used to form an electroplated structure in accordance with one embodiment of the present claimed invention. 
     FIGS. 2A-2F are side sectional views of process steps used to form an electroplated structure in accordance with another embodiment of the present claimed invention. 
     FIG. 3 is a flow chart of steps performed in accordance with one embodiment of the present claimed invention. 
     FIGS. 4A-4E are side sectional views of process steps used to form a dual layer black matrix structure in accordance with another embodiment of the present claimed invention. 
     FIG. 5 is a flow chart of steps performed in accordance with one embodiment of the present claimed invention. 
    
    
     The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     With reference now to FIGS. 1A-1F, side sectional views of process steps used to form an electroplated structure in accordance with the present claimed invention are shown. Referring specifically to FIG. 1A, a side-sectional view of a starting point in the formation of an electroplated structure is shown. The following detailed description of the process steps of FIGS. 1A-1F, will pertain to the formation of an electroplated focus waffle as well as to the formation of an electroplated black matrix. Hence, as will be set forth below, the process steps of the present embodiment are adapted for use in forming an electroplated focus waffle and/or an electroplated black matrix. Although portions of the present embodiment refer to a black matrix, it will be understood that the term “black” refers to the opaque, low reflectivity characteristic of the matrix. Thus, the present invention is also well suited to having a color other than black. 
     With reference to FIG. 1A, the present embodiment begins with underlying structure  100 . In one embodiment (e.g. an embodiment which forms an electroplated black matrix, “a black matrix embodiment”), underlying structure  100  is a faceplate of, for example, a flat panel display device. In another embodiment, (e.g. an embodiment which forms an electroplated focus waffle, “a focus waffle embodiment”), underlying structure  100  is a cathode of, for example, a flat panel display device such as a field emission display device. 
     Referring next to FIG. 1B, the present embodiment then forms molded structures over selected portions  104  of the flat panel display device. In the present embodiments, the molded structures are comprised of structures  102  of photosensitive material such as photoresist. In one embodiment, the photoresist is deposited, masked, exposed, and the unexposed photoresist is then rinsed to form structures  102  at desired locations. As shown in FIG. 1B, structures  102  are formed overlying regions  104  and are not formed above regions  106 . In the black matrix embodiment, regions  104  are sub pixel regions, and regions  106  are regions disposed between sub-pixel regions  104 . Furthermore in the black matrix embodiment, structures  102  have a height of approximately  50  microns. In a focus waffle embodiment, regions  104  are electron emitting portions of a field emission display device, and regions  106  are regions between electron emitting portions of the field emission display device. Additionally, in the focus waffle embodiment, structures  102  have a height of approximately 40-60 microns. Although such specific dimensions and materials will be recited in the present application, it will be understood that these dimensions and materials are exemplary and that the present invention is well suited to the use of various other dimensions and materials. 
     With reference now to FIG. 1C, in the present embodiments, an electroplating seed layer  108  is then deposited over structures  102  and regions  106 . Electroplating seed layer  108  of the present embodiment is a double-layer of material which is sputter-coated over structures  102  and regions  106 . In one embodiment, electroplating seed layer  108  is comprised of an initial opaque, low reflectivity sputter-coated layer of, for example, “black chrome”, followed by the deposition of an electroplating-conducive material. Such electroplating-conducive material is comprised, for example, of nickel, gold, copper, silver, chrome, and the like. In one embodiment, electroplating seed layer  108  is formed having a thickness of approximately 1000 Angstroms. Additionally, in the black matrix embodiment, electroplating seed layer  108  does need to have a first opaque, low reflectivity layer. 
     Referring now to FIG. 1D, after the deposition of electroplating seed layer  108 , the present embodiment deposits second molded structures  110  on respective top surfaces of photoresist structures  102 . In the present embodiments, the second molded structures are comprised of sections of photosensitive material such as photoresist. In one embodiment, the photoresist comprising the second molded structures is deposited, masked, exposed, and the unexposed photoresist is then rinsed to leave second molded structures  110  on the respective top surfaces of photoresist structures  102 . In one embodiment second molded structures  110  have a thickness of approximately 5-10 microns. 
     Next, as shown at FIG. 1E, the present embodiments electroplate of layer of material  112  onto portions of electroplating seed layer  108  such that an electroplated structure is formed at desired regions of the flat panel display device. More specifically, the structure of FIG. 1D has a potential applied thereto and is dipped in an aqueous solution of the material to be electroplated. The material to be electroplated to form electroplated layer  112  is, for example, nickel, gold, copper, silver, chromium, and the like. As shown in FIG. 1E, because second molded structures  110  are not conductive, substantially no material is electroplated thereon during the electroplating process. Hence, electroplated layer  112  is formed on electroplating seed layer  108  except for those portions of electroplating seed layer  108  which are covered by second molded structures  110 . Thus, the respective top surfaces of structures  102  have little or no material electroplated thereover. Furthermore, in the present embodiment, electroplated layer  112  has a thickness of approximately 5-10 microns. 
     With reference now to FIG. 1F, the present embodiments then remove second molded structures  110  from respective top surfaces of photoresist structures  102 . Removal of second molded structures  110  is accomplished using a photoresist removal process. The present embodiments then remove those portions of electroplating seed layer  108  which were residing beneath second molded structures  110  using an etchant (or etchants) corresponding to the material (or materials) comprising electroplating seed layer  108 . Additionally, as shown in FIG. 1F, the present embodiments also remove photoresist structures  102  (using another photoresist removal process) such that a cavity  114  partially encapsulated by electroplated layer  112  (and underlying electroplating seed layer  108 ) remains. In a black matrix embodiment, cavity  114  is adapted to have sub-pixel forming material deposited therein. In a focus waffle embodiment, the remaining electroplated layer  112  forms walls which are adapted to focus electrons emitted by field emitters within the field emission display device. Hence, the present embodiments provide an electroplated black matrix and/or an electroplated focus waffle without requiring the use of expensive and contaminant producing polyimide material. Thus, the electroplated structure of the present embodiments is cheaper and cleaner than existing products. 
     As yet another advantage of the present embodiments, remaining portions of electroplated layer  112  can also be used to buttress support structures of the flat panel display device. For example, a support wall can reside above region  106  of the present embodiments. Furthermore, although remaining portions of electroplated layer  112  may appear “dome-shaped” above regions  104 , the present embodiments are well suited to varying the shape of structures  102  and, thus, create remaining portions of electroplated layer  112  with a greater or lesser amount of curvature. In one embodiment, the curved shape of remaining portions of electroplated layer  112  helps to reflect electrons back towards the sub-pixel regions. Also, the conductive nature of remaining portions of electroplated layer  112  insures efficient bleeding of excess charges when desired. 
     With reference to FIGS. 2A-2F, side sectional views illustrating steps performed in accordance with other embodiments of the present invention are shown. As shown in FIG. 2A, the present embodiment begins with underlying structure  200 . In one embodiment (e.g. an embodiment which forms an electroplated black matrix, “a black matrix embodiment”), underlying structure  200  is a faceplate of, for example, a flat panel display device. In another embodiment, (e.g. an embodiment which forms an electroplated focus waffle, “a focus waffle embodiment”), underlying structure  200  is a cathode of, for example, a flat panel display device such as a field emission display device. 
     Referring still to FIG. 2A, the present embodiment then forms a thin film black matrix  202  over underlying structure  200 . As shown in FIG. 2B, portions of thin film black matrix  202  are formed overlying regions  206  and are not formed above regions  204  and  208 . In the black matrix embodiment, regions  204  and  208  are sub pixel regions and support structure regions, respectively. That is, in such an embodiment, a sub-pixel will subsequently be formed above region  204  and a support structure will be disposed above region  208 . Regions  206  are regions above which will be formed an electroplated black matrix In a focus waffle embodiment, region  204  resides above electron emitting portions of a field emission display device, and regions  208  are regions between electron emitting portions of the field emission display device which may have support structures disposed thereover. Regions  206 , in such an embodiment, are regions above which will be formed an electroplated focus waffle. 
     Referring next to FIG. 2B, the present embodiment then forms molded structures over selected portions  204  and  208  of the flat panel display device. In the present embodiments, the molded structures are comprised of pads  210  of photosensitive material such as photoresist. In one embodiment, the photoresist is deposited, masked, exposed, and the unexposed photoresist is then rinsed to form pads  210  at desired locations. 
     In one black matrix embodiment, the photosensitive material, after deposition above the entire surface of underlying structure  200  (including above thin film black matrix  202 ), is then exposed to light from the exterior surface of underlying structure  200  (a faceplate in this embodiment). By exposing the photosensitive material to light from the exterior surface of the faceplate, thin film black matrix  202  masks those portions of the photosensitive material which reside above thin film black matrix  202 . As a result, those portions of photosensitive material which reside above thin film black matrix  202  are prevented from being exposed. Thus, only the photosensitive material residing above regions  204  and  208  is cured. 
     As shown in FIG. 2B, pads  210  are formed overlying regions  204  and  208  and are not formed above regions  206  (i.e. pads  210  are not formed  2 D above thin film black matrix  202 ). Additionally, in the present embodiments, photoresist pads  210  have vertically oriented side surfaces and a horizontally oriented top surface. In the black matrix embodiment, photoresist pads  210  have a height of approximately 50 microns. In the focus waffle embodiment, photoresist pads  210  have a height of approximately 40-60 microns. Although such specific dimensions and materials will be recited in the present application, it will be understood that these dimensions and materials are exemplary and that the present invention is well suited to the use of various other dimensions and materials. 
     With reference now to FIG. 2C, in the present embodiments, an electroplating seed layer  212  is then deposited over photoresist pads  210  and above thin film black matrix  206 . Electroplating seed layer  212  of the present embodiments is comprised of material which is sputter-coated over photoresist pads  210  and above thin film black matrix  202 . In one embodiment, electroplating seed layer  212  is comprised of an initial opaque, low reflectivity sputter-coated layer of, for example, “black chrome”, followed by the deposition of an electroplating-conducive material. Such electroplating-conducive material is comprised, for example, of nickel, gold, copper, silver, chromium, and the like. In one embodiment, electroplating seed layer  212  is formed having a thickness of approximately 1000 Angstroms. Additionally, in the focus waffle embodiment, electroplating seed layer  212  does need to have a first opaque, low-reflectivity layer. 
     Referring now to FIG. 2D, the present embodiments then remove electroplating seed layer  212  from the horizontally oriented top surfaces of photoresist pads  210 . As shown in FIG. 2D, the present embodiment also remove electroplating seed layer  212  from the top surface of thin film black matrix  202 . In one embodiment, electroplating seed layer  212  is removed from the aforementioned horizontally oriented top surfaces using a directional dry etch such as, for example, a reactive-ion etch. As a result, electroplating seed layer  212  remains on the vertically oriented surfaces of photoresist pads  210 . 
     Next, as shown at FIG. 2E, the present embodiments electroplate of layer of material  214  onto the remaining portions of electroplating seed layer  212  such that an electroplated structure is formed at desired regions of the flat panel display device. Moreover, the present embodiments electroplate material onto the vertically-oriented, electroplating seed layer-coated, side surfaces of photoresist pads  210  without substantially electroplating material onto the horizontally oriented top surface of photoresist pads  210 . More specifically, the structure of FIG. 2D has a potential applied thereto and is dipped in an aqueous solution of the material to be electroplated. The material to be electroplated to form electroplated layer  214  is, for example, nickel, gold, copper, silver, chrome, and the like. Because electroplating seed layer  212  remains only on the vertically oriented surfaces of photoresist pads  210  after the etching process illustrated in FIG. 2D, remaining portions of electroplating seed layer  212  function as an “electroplating frame”. That is, the electroplating process is confined to the area between the electroplating seed layer-coated vertically oriented side surfaces of photoresist pads  210 . Hence, in the present embodiment, the electroplating process is controlled and confined by previous easily and accurately controllable manufacturing steps used to form photoresist pads  210 . 
     With reference now to FIG. 2F, the present embodiments then remove photoresist pads  210  (using a photoresist removal process) such that cavities  216 ,  218 , and  220  partially encapsulated by electroplated layer  214  (and underlying electroplating seed layer  212 ) remains. In a black matrix embodiment, a portion of the cavities (e.g. cavities  216  and  220 ) is adapted to have sub-pixel forming material deposited therein. A second portion of the cavities (e.g. cavities  218 ) are adapted to have a support structure disposed therein. In a focus waffle embodiment, a portion of the cavities (e.g. cavities  216  and  220 ) is adapted to focus electrons emitted by field emitters within the field emission display device. A second portion of the cavities (e.g. cavities  218 ) are adapted to have a support structure disposed therein. Hence, the present embodiments provide an electroplated black matrix and/or an electroplated focus waffle without requiring the use of expensive and contaminant producing polyimide material. Thus, the electroplated structure of the present embodiments is cheaper and cleaner than existing products. In one embodiment, a polishing step is also performed to achieve uniform height. 
     As yet another advantage of the present embodiments, remaining portions of electroplated layer  212  can also be used to buttress support structures of the flat panel display device. For example, a support wall can reside above region  208  of the present embodiments. Also, the conductive nature of remaining portions of electroplated layer  212  insures efficient bleeding of excess charges when desired. 
     Referring now to FIG. 3, a flow chart  300  succinctly setting forth the aforementioned steps of one embodiment of the present invention is shown. At step  302 , the present invention forms molded structures over selected portions of a flat panel display device. 
     Next, at step  304 , the present invention deposits an electroplating seed layer over the molded structures formed at step  302 . 
     Referring now to step  306 , the present invention then electroplates material onto portions of the electroplating seed layer which was deposited at step  304 . In so doing, the present invention forms an electroplated structure for a flat panel display device. As shown in step  306 , in one embodiment, a polishing step is also performed to achieve uniform height. 
     With reference now to FIGS. 4A-4E, side sectional views of process steps used to form a dual layer electroplated structure in accordance with the present claimed invention are shown. Referring specifically to FIG. 4A, a side-sectional view of a starting point in the formation of a dual layer electroplated structure is shown. The following detailed description of the process steps of FIGS. 4A-4E, will pertain to the formation of a dual layer electroplated focus waffle as well as to the formation of a dual layer electroplated black matrix. Hence, as will be set forth below, the process steps of the present embodiment are adapted for use in forming a dual layer electroplated focus waffle and/or a dual layer electroplated black matrix. Although portions of the present embodiment refer to a dual layer black matrix, it will be understood that the term “black” refers to the opaque, low reflectivity characteristic of the matrix. Thus, the present invention is also well suited to having a color other than black. 
     With reference to FIG. 4A, the present embodiment begins with underlying structure  400 . In one embodiment (e.g. an embodiment which forms a dual layer electroplated black matrix, “a dual layer black matrix embodiment”), underlying structure  400  is a faceplate of, for example, a flat panel display device. In another embodiment, (e.g. an embodiment which forms a dual layer electroplated focus waffle, “a dual layer focus waffle embodiment”), underlying structure  400  is a cathode of, for example, a flat panel display device such as a field emission display device. 
     Referring still to FIG. 4A, the present embodiment then deposits an initial opaque, low reflectivity sputter-coated layer  402  of, for example, “black chrome”. In the present embodiment, a layer  404  of photosensitive material such as photoresist is then deposited above layer  402 . In one embodiment, the black chrome layer is comprised of a dual layer of, for example, underlying black chrome and an overlying conductive layer. 
     With reference now to FIG. 4B, layer  404  of photoresist is deposited, masked, exposed, and the unexposed photoresist is then rinsed to form structures  404   a ,  404   b , and  404   c  at desired locations. As shown in FIG. 4B, structures  404   a ,  404   b , and  404   c  are formed overlying desired regions of layer  402  and substrate  400 . Additionally, openings  406   a ,  406   b , and  406   c  are formed are formed above regions  402   a ,  402   b , and  402   c  of layer  402 . In the black matrix embodiment, regions underlying structures  404   a ,  404   b , and  404   c  are sub pixel regions, and regions  406   a ,  406   b , and  406   c  are regions disposed between sub-pixel regions. Furthermore in the black matrix embodiment, structures  404   a ,  404   b , and  404   c  have a height of approximately  50  microns. 
     Referring still to FIG. 4B, in a focus waffle embodiment, regions underlying structures  404   a ,  404   b , and  404   c  are electron emitting portions of a field emission display device, and regions  406   a ,  406   b , and  406   c  are regions disposed between electron emitting portions of the field emission display device. Additionally, in the focus waffle embodiment, structures  404   a ,  404   b , and  404   c  have a height of approximately 40-60 microns. Although such specific dimensions and materials will be recited in the present application, it will be understood that these dimensions and materials are exemplary and that the present invention is well suited to the use of various other dimensions and materials. 
     Next, as shown at FIG. 4C, the present embodiment electroplates material onto exposed regions  402   a ,  402   b , and  402   c  of black chrome layer  402  such that electroplated structures  408   a ,  408   b , and  408   c  are formed at desired regions of the flat panel display device. More specifically, in one embodiment, the structure of FIG. 4B has a potential applied thereto and is dipped in an aqueous solution of the material to be electroplated. The material to be electroplated to form electroplated structures  408   a ,  408   b , and  408   c  is, for example, nickel, gold, copper, silver, chromium, and the like. As shown in FIG. 4C, because photoresist structures  404   a ,  404   b , and  404   c  are not conductive, substantially no material is electroplated thereon during the electroplating process. Furthermore, in the present embodiment, electroplated structures  408   a ,  408   b , and  408   c  typically have a height of approximately 40-60 microns. 
     With reference now to FIG. 4D, the present embodiment then removes photoresist structures  404   a ,  404   b , and  404   c  from respective regions  402   d ,  402   e , and  402   f  of black chrome layer  402 . Removal of photoresist structures  404   a ,  404   b , and  404   c  is accomplished using a photoresist removal process. 
     Referring now to FIG. 4E, the present embodiment then removes black chrome layer  402  from respective regions  402   d ,  402   e , and  402   f . As a result, dual layer structures (comprised at the base of regions  402   a ,  402   b , and  402   c , with overlying electroplated material  408   a ,  408   b , and  408   c , respectively) are left formed above substrate  400 . In a black matrix embodiment, the regions between the electroplated structures are adapted to have sub-pixel forming material deposited therein. In a focus waffle embodiment, the electroplated structures focus electrons emitted by field emitters within the field emission display device. Hence, the present embodiment provides an electroplated dual layer black matrix and/or an electroplated dual layer focus waffle without requiring the use of expensive and contaminant producing polyimide material. Thus, the dual layer electroplated structure of the present embodiments is cheaper and cleaner than existing products. 
     Referring now to FIG. 5, a flow chart  500  succinctly setting forth the aforementioned steps of the above-described dual layer embodiment of FIGS. 4A-4E is shown. At step  502 , the present embodiment deposits a base metal film onto a substrate. In one embodiment, the black chrome layer is comprised of a dual layer of, for example, underlying black chrome and an overlying conductive layer. 
     Next, at step  504 , the present embodiment applies and patterns a photoresist material formed at step  502 . 
     Referring now to step  506 , the present embodiment then electroplates material onto portions of the exposed base metal film which was deposited at step  502 . In so doing, the present embodiment forms dual layer electroplated structures for use in a flat panel display device. 
     At step  508 , the present embodiment removes remaining portions of the photoresist material which were deposited at step  504 , such that the dual layer electroplated structures formed at step  506  remain above the substrate. 
     With reference next to step  510 , the present embodiment then removes the base metal film which was residing beneath the photoresist structures formed at step  504  such that a dual layer structure for use in a field emission display is formed. 
     Thus, the present invention provides, in one embodiment, a structure on the display cathode which effectively directs electrons emitted from electron emitters. The present invention provides, in another embodiment, a structure on the faceplate which effectively separates neighboring phosphor sub-pixels. The present invention, in each of the above-mentioned embodiments, achieves the above-listed accomplishments without requiring the use of expensive and contaminant producing polyimide material. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.