Abstract:
A component having an airdome enclosure that protects the component from its external environment. An airdome enclosure according to the present techniques avoids the high costs of employing special materials and/or specialized process steps in the manufacture of a component. An electronic component according to the present techniques includes a set of substructures formed on a substrate and an airdome enclosure over the substructures that protects the substructures and that hinders the formation of parasitic capacitances among the substructures.

Description:
BACKGROUND 
     A variety of components, e.g. electronic components and mechanical components, may include a coating of material for protecting the component from its external environment. For example, an electronic component may be applied with a plastic molding material during manufacture that provides moisture protection for the electronic component as well as provide electrical isolation among subcomponents of the electronic component. 
     A protective coating material on an electronic component may possess dielectric properties that may adversely affect the operation of the electronic component. For example, a plastic molding material may have a relatively high dielectric constant. A material with a relatively high dielectric constant may cause the formation of relatively high parasitic capacitances among the subcomponents of an electronic component. Unfortunately, high levels of parasitic capacitances among the subcomponents of an electronic component may adversely affect the operation of the electronic component. For example, parasitic capacitances may adversely affect the frequency response of an electronic component. 
     One prior technique for minimizing the undesirable parasitic capacitances in an electronic component caused by a protective coating is to employ a coating material having a relatively low dielectric constant. For example, composite materials or porous plastic materials having a relatively low dielectric constant may be employed to protect an electronic component. Unfortunately, composite materials and porous plastic materials may increase the costs of manufacturing an electronic component by imposing additional steps on the manufacturing process. 
     SUMMARY OF THE INVENTION 
     A component is disclosed having an airdome enclosure that protects the component from its external environment. An airdome enclosure according to the present techniques avoids the high costs of employing special materials and/or specialized process steps in the manufacture of a component. 
     An electronic component according to the present technique includes a set of substructures for the electronic component formed on a substrate and an airdome enclosure over the substructures that protects the electronic component. The airdome enclosure includes air spaces that isolate the substructures while hindering the formation of parasitic capacitances among the substructures. 
     Other features and advantages of the present invention will be apparent from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with respect to particular exemplary embodiments thereof and reference is accordingly made to the drawings in which: 
         FIG. 1   a – 1   b  illustrate the formation of an electronic component that includes an airdome enclosure according to the present teachings; 
         FIG. 2  is a cut-away perspective view of an electronic component that shows a set of dielectric regions that form seals in the gaps; 
         FIG. 3  shows an embodiment that includes a pair of valleys formed in a top substructure that impede movement of dielectric material into the air spaces. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1   a – 1   b  illustrate the formation of an electronic component  10  that includes an airdome enclosure according to the present teachings. The airdome enclosure of the electronic component  10  protects the electronic component  10  and forms a set of air spaces  29  and  30  that provide electrical isolation among the subcomponents of the electronic component  10 . The relatively low dielectric constant associated with the air in the air spaces  29  and  30  hinder the formation of undesirable parasitic capacitances among the subcomponents of the electronic component  10 . 
     The electronic component  10  is formed onto a substrate  11 . Example materials for the substrate  11  include silicon and gallium-arsenide. Other substrate materials include metal, plastic, circuit board materials, organic film, etc. 
     The electronic component  10  includes a series of layers deposited onto the substrate  11 . The layer materials deposited onto the substrate  11  may be selected and patterned into the particular subcomponents for the electronic component  10 . For example, the layers may be deposited and patterned to form transistor subcomponents, capacitor subcomponents, resistor subcomponents, etc., depending on the particular design of the electronic component  10 . The materials of these layers may include any combination of metal and dielectric materials. 
     In one embodiment, the series of layers deposited onto the substrate  11  include a first, a second, and a third metal layer. Example methods for forming the metal layers include evaporation, sputtering, and plating. 
     The first metal layer is patterned into a set of metal structures  12 ,  13 , and  14 . The second metal layer is patterned into a set of metal structures  15  and  16 . 
     A dielectric material is deposited over the metal structures  12 – 16  and patterned to form what will be the air spaces  29  and  30  and then the third metal layer is deposited over the dielectric material that covers the metal structures  12 – 16 . The third metal layer is then patterned into a set of metal structures  17 ,  18 , and  19 . The dielectric material is then removed to reveal the air spaces  29  and  30 . The dielectric material deposited over the metal structures  12 – 16  and patterned to form what will be the air spaces  29  and  30  may be a photo-resist or some other type of dielectric material. 
     The patterning of the third metal layer forms a ledge  20  on the structure  17  and a ledge  21  on the structure  18  with an air gap  40  in between the ledges  20  and  21 . The patterning of the third metal layer also forms a ledge  22  on the structure  18  and a ledge  23  on the structure  19  with an air gap  42  in between the ledges  22  and  23 . The air gaps  40 – 42  may be formed to the most narrow possible gap width given the process technology used to form the electronic component  10 . In one embodiment, the width of each air gap  40 – 42  is between 1 and 3 microns. 
     A dielectric overcoat is then deposited onto the electronic component  10  to form a set of dielectric films  26 – 28 . The dielectric films  26 – 28  form a seal  70  in the air gap  40  and a seal  72  in the air gap  42  but do not fill in the air spaces  29 – 30 . Example materials for the dielectric overcoat include silicon-dioxide, silicon-nitride, or a combination of silicon-dioxide and silicon-nitride, a plastic molding compound, or an organic molding compound. 
     The dielectric overcoat may be deposited using a dry process in which a gas reaction is used to form the dielectric material. The dielectric overcoat may be deposited using a wet process in which a liquid form of glass is applied and then heated. The dielectric overcoat may be formed by depositing an organic film followed by a curing step. 
     The width and/or shapes of the air gaps  40 – 42  may be selected to allow the dielectric overcoat to form the seals  70 – 72  while preventing the dielectric overcoat from entering and filling the air spaces  29  and  30 . The widths and/or shapes of the air gaps  40 – 42  may be selected in response to the viscosity of the dielectric overcoat during deposition and/or the process temperature during deposition. The air spaces  29  and  30  may be filled with a air or low pressure gases during the deposition of the dielectric overcoat. 
       FIG. 2  is a cut-away perspective view of the electronic component  10  that shows a set of dielectric regions  50 – 52  of the dielectric overcoat that form seals in the air gaps  40 – 42 . This view also shows a set of dielectric regions  60 – 64  that form seals in openings on the top of the metal structure  18 . The openings on the top of the metal structure  18  may be formed during cleanout of process material. 
       FIG. 3  shows an embodiment in which the third metal layer includes a pair of valleys  80 – 82 . The valleys  80 – 82  are shaped so as to impede the movement of dielectric material through the air gaps  40 – 42  into the air spaces  29  and  30  during formation of the dielectric overcoat. As before, the dielectric material underneath the third metal layer is removed after patterning of the air gaps  40 – 42  to reveal the air spaces  29  and  30 . 
     The valleys  80 – 82  may be shaped by shaping the dielectric material, e.g. a photo-resist, underneath the third metal layer. For example, the V-shaped dips of the valleys  80 – 82  may be formed with a photo-masking step and exposure of the photo-resist. Alternatively, a single photo-mask may be employed with specially designed aperture patterns using OPC (Optical Proximity Correction) algorithms. If a dielectric material is used underneath the third metal layer then that dielectric material may be subjected to a second photo-masking and etching to produce the V-shaped dips for the valleys  80 – 82 . 
     An airdome enclosure according to the present techniques may be used in any type of electronic component including active components and passive components. In addition, an airdome enclosure according to the present techniques may be used for any component, electronic or otherwise, that may benefit from the protection provided from an external environment. 
     The foregoing detailed description of the present invention is provided for the purposes of illustration and is not intended to be exhaustive or to limit the invention to the precise embodiment disclosed. Accordingly, the scope of the present invention is defined by the appended claims.