Patent Publication Number: US-8109607-B2

Title: Fluid ejector structure and fabrication method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims the benefit of U.S. Provisional patent application Ser. No. 61/035,223, filed Mar. 10, 2008, which is hereby incorporated by reference in it&#39;s entirety. 
    
    
     BACKGROUND 
     Thermal inkjet printers typically utilize a printhead that includes an array of orifices (also called nozzles) through which ink is ejected on to paper or other print media. One or more printheads may be mounted on a movable carriage that traverses back and forth across the width of the paper feeding through the printer, or the printhead(s) may remain stationary during printing operations, as in a page width array of printheads. A printhead may be an integral part of an ink cartridge or part of a discrete assembly to which ink is supplied from a separate, often detachable ink container. Ink filled channels feed ink to a firing chamber at each orifice from a reservoir ink source. Applied individually to addressable thermal elements, such as resistors, ink within a firing chamber is heated, causing the ink to bubble and thus expel ink from the chamber out through the orifice. As ink is expelled, the bubble collapses and more ink fills the chamber through the channels from the reservoir, allowing for repetition of the ink expulsion sequence. 
     Many conventional thermal inkjet printheads are currently produced with ink feed channels formed in a semiconductor substrate structure that includes the firing resistors. A barrier layer is formed on the substrate structure and a metal or polyimide (e.g., Kapton®) orifice plate is attached to the barrier layer. The ink feed channels carry ink to openings in the barrier layer that direct ink to the resistors and partially define the firing chamber volume for each resistor. The barrier layer material is usually a thick, organic photosensitive material laminated onto the substrate structure, and then patterned and etched with the desired opening and chamber configuration. The orifice plate provides the ink ejection/expulsion path for the firing chambers. Metal and polyimide orifice plate materials and organic barrier layer materials, however, can be susceptible to corrosion from printing inks, thus potentially limiting the ink chemistry options for better printing performance 
     Also, during printhead fabrication, aligning and attaching the orifice plate to the barrier layer on the substrate structure requires special precision and special adhesives. If the orifice plate is warped or dimpled, or if the adhesive does not correctly bond the orifice plate to the barrier layer, poor control of the ink drop trajectory may result. Often, individual orifice plates must be attached at single printhead die locations on a semiconductor substrate wafer/structure that contains many such die locations. It is desirable, of course, for increasing productivity as well as helping ensure proper orifice plate alignment to have a fabrication process that allows for placement of a single orifice plate over the entire substrate structure to cover all of the printhead die locations. Some efforts to fabricate orifice plates from a deposited dielectric material have met with only limited success due to high dielectric deposition temperatures and large built-in stresses for thick dielectric layers. 
    
    
     
       DRAWINGS 
         FIGS. 1 and 2  are elevation and perspective section views, respectively, illustrating a thermal inkjet printhead structure according to one embodiment of the disclosure. 
         FIG. 3  is a detail section view of a portion of the printhead structure shown in  FIG. 1 . 
         FIGS. 4-8  are elevation section views illustrating one embodiment of a method for fabricating a thermal inkjet printhead structure such as the one shown in  FIGS. 1 and 2 . 
         FIGS. 9-11  are elevation section views illustrating another embodiment of a method that may be used for fabricating a thermal inkjet printhead structure similar to the one shown in  FIGS. 1 and 2 . 
         FIGS. 12-15  are elevation section views illustrating another embodiment of a method that may be used for fabricating a thermal inkjet printhead structure similar to the one shown in  FIGS. 1 and 2 . 
         FIGS. 16 and 17  are elevation and perspective section views, respectively, illustrating a thermal inkjet printhead structure according to another embodiment of the disclosure. 
         FIG. 18  is a detail section view of a portion of the printhead structure shown in  FIG. 16 . 
         FIGS. 19-27  are elevation section views illustrating one embodiment of a method for fabricating a thermal inkjet printhead structure such as the one shown in  FIGS. 16 and 17 . 
         FIG. 28  illustrates another embodiment of a printhead structure that may be fabricated using the method of  FIGS. 19-27  in which multiple ink channels carry ink to a single firing chamber. 
         FIG. 29  is a detail section view of a portion of the printhead structure shown in  FIG. 28 . 
     
    
    
     The structures shown in the figures, which are not to scale, are presented in an illustrative manner to help show pertinent structural and processing features of the disclosure 
     DESCRIPTION 
     Embodiments of the present disclosure were developed in an effort to improve methods for fabricating thermal inkjet printhead structures and to improve the printhead structures themselves. Embodiments of the disclosure, therefore, will be described with reference to the fabrication of a thermal inkjet printhead structure. Embodiments, however, are not limited to thermal inkjet printhead structures, or even inkjet printhead structures in general, but may include other fluid ejector structures and fabrication methods for such ejector structures. Hence, the following description should not be construed to limit the scope of the disclosure. 
       FIGS. 1 and 2  are elevation and perspective section views, respectively, illustrating a thermal inkjet printhead structure  10  according to one embodiment of the disclosure. Inkjet printhead structure  10  represents more generally a fluid-jet precision dispensing device or fluid ejector structure for precisely dispensing a fluid, such as ink, as described in more detail below.  FIG. 3  is a detail section view of a portion of printhead structure  10  within the circle shown in  FIG. 1 . Referring to  FIGS. 1-3 , printhead structure  10  is formed as a composite structure that includes an orifice sub-structure  12  and an ejector element sub-structure  14  bonded together along a bonding interface  16 . As described in more detail below, a direct contact bond is formed between the two sub-structures  12  and  14  at bonding interface  16  using, for example, low temperature plasma activated bonding techniques. Direct contact bonding occurs when two smooth surfaces are brought into direct contact with one another under conditions that allow bonding between the two surfaces at near room temperature. Plasma activation increases the density of the chemical interface species so a robust covalent bond may be achieved at low temperature. Annealing the plasma activated bond increases bond strength. 
     While this Description is at least substantially presented herein to inkjet-printing devices that eject ink onto media, those of ordinary skill within the art can appreciate that embodiments of the present disclosure are more generally not so limited. In general, embodiments of the present disclosure pertain to any type of fluid-jet precision dispensing device or ejector structure for dispensing a substantially liquid fluid. A fluid-jet precision dispensing device is a drop-on-demand device in which printing, or dispensing, of the substantially liquid fluid in question is achieved by precisely printing or dispensing in accurately specified locations, with or without making a particular image on that which is being printed or dispensed on. As such, a fluid-jet precision dispensing device is in comparison to a continuous precision dispensing device, in which a substantially liquid fluid is continuously dispensed therefrom. An example of a continuous precision dispensing device is a continuous inkjet printing device. 
     The fluid-jet precision dispensing device precisely prints or dispenses a substantially liquid fluid in that the latter is not substantially or primarily composed of gases such as air. Examples of such substantially liquid fluids include inks in the case of inkjet printing devices. Other examples of substantially liquid fluids include drugs, cellular products, organisms, chemicals, fuel, and so on, which are not substantially or primarily composed of gases such as air and other types of gases. Therefore, while the following description is described in relation to an inkjet printhead structure for ejecting ink onto media, embodiments of the present disclosure more generally pertain to any type of fluid-jet precision dispensing device or fluid ejector structure for dispensing a substantially liquid fluid as has been described in this paragraph and the preceding paragraph. 
     Firing resistors  18  in ejector element sub-structure  14  are formed as part of a thin film stack  20  on a substrate  22 . Although a silicon substrate  22  is typical, other suitable substrate materials could be used. In addition to firing resistors  18 , thin-film stack  20  usually also will include layers/films that electrically insulate resistors  18  from surrounding structures, provide conductive paths to resistors  18 , and help protect against contamination, corrosion and wear (such protection is often referred to passivation). In the embodiment shown, as best seen in  FIG. 3 , film stack  20  includes a field oxide layer  24  on substrate  22 , a glass layer  26  (typically phosphosilicate glass (PSG)) on field oxide  24 , and a passivation dielectric layer  28  over resistors  18  and glass layer  26 . The specific configuration of film stack  20  is not important to the innovative aspects of this disclosure except that the exposed surface of film stack  20  along direct contact bonding interface  16  must be suitable for bonding to a mating surface on orifice sub-structure  12 . Suitable direct contact bond interface materials are discussed below with regard to the fabrication method illustrated in  FIGS. 4-8 . 
     Channels  30  in substrate  22  carry ink to ink feed slots  32  that extend through film stack  20  near resistors  18 . Ink enters a firing chamber  34  associated with each firing resistor  18  through a corresponding feed slot  32 . Ink drops are expelled or “fired” from each chamber  34  through an orifice  36  in orifice sub-structure  12 . Orifice sub-structure  12  may include a dielectric or other suitable passivation layer  38  along those areas exposed to ink, for example at firing chambers  34  and orifices  36 . 
       FIGS. 4-8  are elevation section views illustrating one embodiment of a method for fabricating printhead structure  10  shown in  FIGS. 1 and 2 . The individual processing techniques that may be used to carry out the methodology described below are conventional techniques well known to those skilled in the art of printhead fabrication and semiconductor processing. Thus, the details of those techniques are not included in the description. For example, semiconductor wafer processing in general, including printhead fabrication, sometimes includes photolithographic masking and etching. This process consists of creating a photolithographic mask containing the pattern of the component to be formed, coating the structure with a light-sensitive material called photoresist, exposing the photoresist coated structure to ultra-violet light through the mask to soften or harden parts of the photoresist, depending on whether positive or negative photoresist is used, removing the softened parts of the photoresist, etching to remove the materials left unprotected by the photoresist, and stripping the remaining photoresist. This photolithographic masking and etching process is referred to herein as “masking and etching.” Other patterning techniques may also be used in the selective removal of materials, thus the process may be referred to more generally as “patterning and etching.” Although it is expected that the selective removal of materials will often involve patterning and etching, other selective removal processes could be used. Hence, references to patterning and etching should not be construed to limit the processes that may be used for the selective removal of material. 
     Referring first to  FIG. 4 , an orifice substrate  40  is patterned and etched along an orifice area  42  to form the desired configuration for the firing chambers  34 , orifices  36  and bonding interface  16  shown in  FIGS. 1 and 2 . Depending on the material used for substrate  40 , it may be necessary or desirable to form a passivation layer  44  on substrate  40  along orifice area  42  to inhibit corrosion from prolonged exposure to ink. For a silicon substrate  40 , for example, passivation layer  44  may be formed by oxidizing the exposed outer surfaces of substrate  40 . 
     Referring to  FIG. 5 , oxide passivation layer  44  is selectively removed to expose silicon substrate  40  and form direct contact bond surfaces  46  using, for example, a buffered oxide etch such as a buffered hydrogen fluoride (HF) etch. The in-process orifice sub-structure shown in  FIG. 4  is designated by part number  48 . Suitable direct contact bond interfaces include oxide to oxide, oxide to silicon, and silicon to silicon. The surface energy of an oxide to silicon bond interface can be nearly twice that of an oxide to oxide bond interface. Thus, oxide bond surfaces on ejector element sub-structure  14  and silicon bond surfaces  46  on orifice sub-structure  12  are expected to yield higher bond strength and, therefore, may be desirable in printhead fabrication. TEOS and other suitable dielectric materials, however, may also be used for orifice substrate bond surfaces  46 . (TEOS refers to the deposition of silicon dioxide using a tetraethylorthosilicate low temperature chemical vapor deposition (TEOS) process.) 
     Referring to  FIG. 6 , in-process orifice sub-structure  48  and an in-process ejector element sub-structure  50  are aligned with one another and direct contact bonded together to form an in-process composite printhead structure  52 . In the embodiment shown, in-process ejector element sub-structure  50  has been processed through the formation of ink slots  32  in thin film stack  20 , but ink channels  30  have not yet been formed in substrate  22 . Also, orifice substrate  40  has not yet been thinned to open orifices  36 . Although these processes might possibly be completed before direct contact bonding, it is preferred to form ink channels  30  and open orifices  36  after bonding to preserve the structural integrity of substrates  22  and  40  during bonding. Processing the comparatively thick, more robust, substrates  22  and  40  shown in  FIG. 6  reduces the risk of damage during alignment and bonding operations. 
     A TEOS passivation layer  28  in film stack  20 , best seen in  FIGS. 2 and 3 , will provide the desired oxide to silicon direct contact bond interface. Also, it is expected that a TEOS passivation layer  28  will provide suitable passivation characteristics for most inkjet printhead applications. A silicon nitride, silicon carbide or other suitable dielectric material, however, may be used for passivation layer  28  depending on the desired direct contact bonding interface and/or passivation characteristics for layer  28 . One or both of direct contact bond surfaces  46  on in-process sub-structure  48  and passivation layer  28  on in-process sub-structure  50  (at locations of bonding interface  16 ) may be planarized, using CMP (chemical mechanical polishing) for example, if necessary or desirable to provide flat, smooth bonding surfaces. A direct contact bond is formed between in-process sub-structures  48  and  50  at bonding interface  16  by, for example, low temperature plasma activated bonding, which is sometimes also referred to as plasma enhanced bonding. 
     The use of low temperature plasmas of various ionized gases to enhance the bonding properties of bond surfaces for direct contact bonding is well known in the art of semiconductor processing. Plasma activated bonding typically involves placing the parts to be bonded into a plasma chamber, introducing a gas or mixture of gases into the chamber, and energizing the gas to produce a plasma by exposing the gas to radio frequency electromagnetic radiation. The bond surfaces are held in close proximity to one another as they are exposed to the plasma and then pressed together to bond. The bonded parts may be annealed as necessary or desirable to strengthen the bond. Although a variety of different gases may be used depending on the characteristics of the bond surfaces, it is expected that nitrogen (N 2 ) and oxygen (O 2 ) gases will induce suitable bonding between a silicon bond surface  46  on orifice sub-structure  48  and an oxide surface (passivation layer  28 ) on printhead sub-structure  52 . In one example, exposing the bond surfaces  46  and  28  to an N 2  plasma at 100 watts RF power for 30 seconds will induce the activation needed to form an adequate bond. The parts are then heated to about 250° C. for approximately one hour to anneal the bond area and improve bond strength. Annealing at this temperature is significant below a typical CMOS thermal budget of 425° C. but it is sufficiently high for direct, covalent bonding two planarized dielectric surfaces. 
     Referring now to  FIG. 7 , orifice substrate  40  is removed to the level of passivation layer  44  at the orifice locations by, for example, back grinding the silicon substrate  40  until reaching the oxide passivation layer  44 . Although an additional cleaning step may be necessary or desirable in some circumstances following back grinding to remove any waste particles, it is expected that the deionized (DI) water rinse will usually be sufficient. Referring to  FIG. 8 , ejector sub-structure substrate  22  is patterned and etched to form ink channels  30  with, for example, a laser or dry reactive ion etch. In the embodiment of in-process ejector sub-structure  50  shown in  FIGS. 6-8 , substrate  22  is patterned for the ink channel etch with an oxide layer  54  formed on the backside of substrate  22  prior to direct contact bonding. In other embodiments, it may be desirable to pattern substrate  22  for the channel etch after bonding with, for example, photolithographic masking. As best seen by comparing  FIGS. 1 and 8 , passivation layer  44  is then removed at each orifice location to open orifices  36  by, for example, planarizing the top surface of orifice substrate  30  to the thickness of layer  44  (using CMP for example) or by etching away the exposed oxide passivation layer  44 , but not allowing the etch to continue into the firing chambers  34 , leaving a passivation layer  38  in those areas exposed to ink as shown in  FIGS. 1 and 2 . 
     The inorganic covalent bonds bonding together the ejector and orifice sub-structures of printhead structure  10  eliminate the problematic organic barrier and adhesive layers in conventional printheads that are susceptible to ink attack, thus providing a firing chamber solution with wide ink latitude that is largely inert to even aggressive solvents. The direct bonding fabrication method described above enables the low-temperature/low-stress wafer level attachment of a pre-fabricated dielectric orifice sub-structure and a nearly fully processed thermal ejector element sub-structure. 
     In another embodiment illustrated in  FIGS. 9-11 , the direct contact bond is made between an oxide layer  44  on orifice sub-structure  12  and a TEOS layer  28  on ejector element sub-structure  14 . Referring to  FIG. 9 , a silicon orifice substrate  40  is patterned and etched along an orifice area  42  to form the desired configuration for the firing chambers  34 , orifices  36  and bonding interface  16 , and the silicon substrate  40  is oxided to form an oxide passivation layer  44 . Referring to  FIG. 10 , in-process orifice sub-structure  48  and an in-process ejector element sub-structure  50  are aligned with one another and direct contact bonded together to form an in-process composite printhead structure  52 . In this embodiment, oxide layer  44  is not removed from direct contact bonding surfaces  46  on orifice substrate  40  and, consequently, an oxide-to-oxide bond is formed rather than a silicon-to-oxide bond as in the first embodiment. Referring to  FIG. 11 , orifice substrate  40  is thinned to open orifices  36  using, for example, a grinding operation. 
     In another embodiment illustrated in  FIGS. 12-15 , a silicon-on-insulator (SOI) wafer is used in the fabrication of orifice sub-structure  12  ( FIGS. 1 and 2 ). Referring to  FIG. 12 , an SOI substrate  40  is patterned and etched along an orifice area  42  to form the desired configuration for the firing chambers  34 , orifices  36  and direct contact bonding interface  16 . This topography etch may stop on the buried oxide layer  43 , or it may continue through oxide layer  43  as shown in  FIG. 12 . Substrate  40  may then be oxidized to form an oxide passivation layer  44 . Oxide layer  44  may be removed at bonding surfaces  46  as in the first embodiment described above or left in place as in the second embodiment described above. Oxide layer  44  is shown as being left in place at bonding surfaces  46  in  FIG. 13 . Referring to  FIG. 13 , in-process orifice sub-structure  48  and an in-process ejector element sub-structure  50  are aligned with one another and direct contact bonded together to form an in-process composite printhead structure  52 . Referring to  FIG. 14 , orifice substrate  40  is ground or otherwise thinned from the back side to near buried oxide layer  43 , a thickness of about 10 μm at the locations for the orifices, for example. Then, with oxide layer  43  as an etch stop, a silicon dry etch, for example, may be used to open orifices  36  as shown in  FIG. 15 . As an alternative, orifice substrate  40  may be ground or otherwise thinned from the back side to stop on buried oxide layer  43  and open orifices  36 . 
       FIGS. 16 and 17  are elevation and perspective section views, respectively, illustrating a thermal inkjet printhead structure  56  according to another embodiment of the disclosure.  FIG. 18  is a detail section view of a portion of printhead structure  56  within the circle shown in  FIG. 16 . Printhead structure  56  is similar to printhead structure  10  shown in FIGS.  1 - 3 —only the configuration of the substrate and ink channels is different. Thus, for convenience, the same part numbers are used to designate the same or similar components in both printhead structure  10  and printhead structure  56 . 
     Referring to  FIGS. 16-18 , printhead structure  56  is formed as a composite structure that includes an orifice sub-structure  12  and an ejector element sub-structure  14  bonded together along a bonding interface  16 . Firing resistors  18  in ejector element sub-structure  14  are formed as part of a thin film stack  20  on a substrate  22 . Although a silicon substrate  22  is typical, other suitable substrate materials could be used. In addition to firing resistors  18 , thin-film stack  20  usually also will include layers/films that electrically insulate resistors  18  from surrounding structures, provide conductive paths to resistors  18 , and help protect against contamination, corrosion and wear (such protection is often referred to passivation). In the embodiment shown, as best seen in  FIG. 18 , film stack  20  includes a field oxide layer  24  on substrate  22 , a glass layer  26  on field oxide  24 , and a passivation dielectric layer  28  over resistors  18  and glass layer  26 . 
     Channels  30  in substrate  22  carry ink to ink feed slots  32  that extend through film stack  20  near resistors  18 . Ink enters a firing chamber  34  associated with each firing resistor  18  through a corresponding feed slot  32 . Ink drops are expelled or “fired” from each chamber  34  through an orifice  36  in orifice sub-structure  12 . Orifice sub-structure  12  may include a dielectric or other suitable passivation layer  38  along those areas exposed to ink, for example at firing chambers  34  and orifices  36 . 
       FIGS. 19-27  are elevation section views illustrating one embodiment of a method for fabricating a thermal inkjet printhead structure, such as printhead structure  56  shown in  FIGS. 16 and 17 . The method illustrated in  FIGS. 19-27  may be used with a new direct bond in-process printhead structure, such as structure  52  shown in  FIG. 7 , or with a conventional in-process printhead structure. Referring first to  FIG. 19 , in-process printhead structure  52  (with layer  44  removed to open orifices  36 ) is temporarily attached to a carrier  58  along the exposed outer surface of in-process orifice sub-structure  48 . Carrier  58  is used to strengthen the in-process structure for subsequent processing. Hence, a glass wafer or other suitably strong, stable substrate may be used for carrier  58 . Carrier  58  is temporarily attached to orifice sub-structure  48  with wax, resist, a double coated adhesive film, or another suitable temporary bonding agent. Some double coated adhesive films, for example, include a permanent bonding pressure sensitive adhesive on one side to attach to carrier  58  and a temporary bond thermal release adhesive on the other side to attach to sub-structure  48 . 
     Referring to  FIG. 20 , ejector substrate  22  is thinned to a desired thickness by, for example, back grinding the silicon substrate  22  until reaching the desired thickness. Referring to  FIG. 21 , the thinned ejector substrate  22  is patterned and etched to form ink channels  30  with, for example, a laser or dry reactive ion etch. Temporarily attaching in-process printhead  52  to carrier  58  allows thinning substrate  22  to 20-200 μm, compared to a conventional fabrication process in which the ejector substrate is about 720 μm. The thinned substrate  22  simplifies the channel etch—instead of cutting through a 700 μm wafer, the ink channels can be etched through a comparatively thin silicon membrane. The thinned substrate  22  allows forming more narrow channels while still maintaining the desired channel aspect ratio. It is expected that a shorter ink path through channels  30  to firing chambers  34  will increase the frequency response of printhead structure  56  compared to the longer wider channels  30  in a printhead structure such as structure  10  shown in  FIGS. 1 and 2 . In printhead structure  56 , one ink channel feeds ink to one slot  32  for two adjacent firing chambers  34  (along the section shown) instead of one channel feeding two slots for four adjacent firing chambers in printhead structure  10 . 
     A carrier wafer  58  may be released from an in-process printhead wafer structure  60  at the “wafer level” following the completion of the printhead structure  56  shown in  FIG. 21 . Alternatively, carrier  58  may be left in place to facilitate further processing. For example, and referring to  FIGS. 22 and 23 , in-process printhead wafer structure  60  may be sawn or otherwise singulated into individual printhead dies  62  while still attached to carrier  58 , as indicated by saw cut lines  64 . Processing may continue with dies  62  attached to carrier  58 , mounting multiple dies  62  to a glass, ceramic or other suitable substrate  66  to form a multi-die printhead module  68  as shown in  FIGS. 24 and 25 . Temporary carrier  58  adds strength to the otherwise fragile dies  62  to help minimize the risk of damaging the dies  62  during these processing operations. In addition, the comparatively thick carrier  58  helps flatten the die assembly to make the die attach process easier. 
     Referring to  FIGS. 26 and 27 , carrier  58  is then released by subjecting each module  68  to a release mechanism appropriate for the temporary bonding agent used to attach carrier  58 . For example, if wax is used as the temporary bonding agent, then carrier  58  may be released by heating. Some temporary bonding agents may require immersing or washing module  68  in a solvent to release carrier  58 . Of course, other release mechanisms are possible depending on the characteristics of the temporary bonding agent used to attach carrier  58 . 
       FIG. 28  illustrates another embodiment of a printhead structure, designated by part number  70 , that may be fabricated using the method of  FIGS. 19-27 .  FIG. 29  is a detail section view of a portion of printhead structure  70 . Referring to  FIGS. 28 and 29 , printhead structure  70  includes multiple ink feed channels  30  that carry ink to a single firing chamber  34 . As noted above with reference to  FIG. 20 , the thinned substrate  22  simplifies the channel etch and allows forming more narrow channels while still maintaining the desired channel aspect ratio. Thus, engineers are afforded greater flexibility in designing printhead structures to achieve robust ink flow with greater frequency response. Thin film stack  20  may extend slightly beyond substrate  22  at each channel  30  such that feed slots  32  are more narrow than channels  30 . This configuration offers additional design flexibility to control the ink flow speed through feed slot  32  and reduce the heat generated by resistor  18 , while independently controlling the ink blow back to help maintain firing chamber efficiency. In the dual channel configuration shown in  FIG. 28 , for example, the size of ink channels  30  may be controlled much more precisely over channel structures formed with conventional fabrication methods, to more precisely control ink flow to the firing chambers  34 . 
     As used in this document, forming one part “over” another part does not necessarily mean forming one part above the other part. A first part formed over a second part will mean the first part formed above, below and/or to the side of the second part depending on the orientation of the parts. Also, “over” includes forming a first part on a second part or forming the first part above, below or to the side of the second part with one or more other parts in between the first part and the second part. 
     As noted at the beginning of this Description, the example embodiments shown in the figures and described above illustrate but do not limit the disclosure. Other forms, details, and embodiments may be made and implemented. Therefore, the foregoing description should not be construed to limit the scope of the disclosure, which is defined in the following claims.