Abstract:
Methods for producing waveguides are disclosed. In one embodiment, a waveguide is produced by depositing a first metal layer on a substrate, depositing a sacrificial material on the first metal layer, depositing a second metal layer on the sacrificial material, the second metal layer contacting the first metal layer and defining therebetween a cavity for the waveguide, the cavity filled with the sacrificial material, and removing the sacrificial material.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This is a divisional of copending application Ser. No. 10/619,920 filed on Jul. 15, 2003, the entire disclosure of which is incorporated into this application by reference.  
     
    
     BACKGROUND  
       [0002]     Waveguides are used in various applications to conduct high frequency signals. The waveguides may be manufactured by machining cavities or passages in metal blocks, plating them, and attaching lids to cover the cavities and passages. This process to produce waveguides may be overly expensive.  
       SUMMARY OF THE INVENTION  
       [0003]     Methods for producing waveguides are disclosed. In one embodiment, a waveguide is produced by depositing a first metal layer on a substrate. Next, a sacrificial material is deposited on the first metal layer. A second metal layer is then deposited on the sacrificial material so that it contacts the first metal layer and defines therebetween a cavity for the waveguide, the cavity filled with the sacrificial material. Finally, the sacrificial material is removed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]     Illustrative embodiments of the invention are illustrated in the drawings, in which:  
         [0005]      FIG. 1  illustrates an exemplary plan view of a waveguide before a sacrificial material has been removed;  
         [0006]      FIG. 2  illustrates a first sectional of the waveguide shown in  FIG. 1 ;  
         [0007]      FIG. 3  illustrates the waveguide shown in  FIGS. 1 and 2  after the sacrificial material has been removed;  
         [0008]      FIG. 4  illustrates a sectional of the waveguide shown in  FIG. 1-3  after the sacrificial material has been removed;  
         [0009]      FIG. 5  illustrates a perspective view of the waveguide shown in  FIGS. 1-4  after the sacrificial material has been removed; and  
         [0010]      FIG. 6  illustrates an exemplary method that may be used to produce the waveguide of  FIGS. 1-5 .  
     
    
     DETAILED DESCRIPTION  
       [0011]     An exemplary embodiment of a waveguide that may be used to conduct high frequency electrical signals is illustrated in  FIGS. 1-5 . As illustrated in  FIG. 6 , the waveguide  102  may be produced by first depositing  600  a first metal layer  104  on a substrate  100 . By way of example, the first metal layer may be gold and may be deposited by sputtering, evaporation, or lamination. Other methods may also be used to deposit the first metal layer  104  on the substrate  100 . In some embodiments, after the first metal layer is deposited  600 , it may then be plated to increase the thickness.  
         [0012]     Next, a sacrificial material  108  is deposited  605  on the first metal layer  104 . Sacrificial material  108  may be deposited by spin coating, spray coating, curtain coating, or other suitable method. The thickness of the sacrificial material  108  may vary depending upon the desired height of the waveguide  102 . As will be described in further detail below, sacrificial material  108  will be removed after the waveguide structure is formed to produce a waveguide  102  that may be used to conduct high frequency electrical signals.  
         [0013]     In one embodiment, after sacrificial material  108  has been deposited  605 , sacrificial material  108  may be patterned to a desired length and width for the waveguide  102 . By way of example, the desired length of the waveguide may be 0.70 times the wavelength (e.g., 2.1 cm for a wavelength of 3 cm) and the desired height of the waveguide may be 0.30 times the wavelength (e.g., 0.9 cm for a wavelength of 3 cm). Other suitable dimensions may also be used.  
         [0014]     The patterning may comprise depositing a mask layer (e.g., aluminum or silicon nitride) on the sacrificial material  108 . A photoresist material may then be spin-coated and patterned on the mask layer. A portion of the mask layer not layered by the photoresist material may then be etched away and the photoresist material may then be removed. Reactive ion etching or other technique may be used to remove the sacrificial material  108  not layered by the mask layer. The mask layer may then be removed. It should be appreciated that in alternate embodiments, other methods may be used to pattern sacrificial material  108  so that it is the desired length and width of waveguide  102 .  
         [0015]     In some embodiments, the first metal layer  104  may also be patterned during the patterning of sacrificial material  108 . Alternately, first metal layer  104  may be patterned prior to the deposition of sacrificial material  108  or may not be patterned. It should be appreciated that first metal layer  104  may span more than the length and width of waveguide  102 .  
         [0016]     After the sacrificial material  108  has been deposited  605 , a second metal layer  106  (e.g., gold) is then deposited  610  on the sacrificial material  108  so that it contacts the first metal layer  104 . The second layer  106  may be deposited by sputtering, evaporation, lamination, or other suitable method. In some embodiments, after the second metal layer  106  is deposited  610 , it may then be plated to increase the thickness. The second metal layer  106  in combination with the first metal layer  104  forms a structure for a waveguide  102  with the cavity of the waveguide  102  being filled by sacrificial material  108 .  
         [0017]     In one embodiment, after the second metal layer  104  has been deposited  610 , the second metal layer  106  may be patterned to the desired width and/or length of waveguide  102 . The second metal layer  106  may be patterned by depositing and patterning a photoresist material on the second metal layer  106  to the desired length and/or width of waveguide  102 . The second metal layer may then be etched. Finally, the photoresist material may be removed. Other methods may also be used to pattern second metal layer  104 . It should be appreciated that in other embodiments, the second metal layer  104  may not be patterned and may span more than the length and/or width of waveguide  102 .  
         [0018]     Finally, after the second metal layer  106  has been deposited  610 , the sacrificial material  108  is removed  615 . In one embodiment, the sacrificial material  108  comprises a material that decomposes at a lower temperature than the first and second metal layers and the sacrificial material  108  may be removed  615  using thermal decomposition. By way of example, the sacrificial material  108  may be polynorbornene and may be decomposed at 425° Celsius at oxygen concentrations below 5 parts per million (ppm). Other suitable materials and temperatures may be used to thermally decompose sacrificial material  108 .  
         [0019]     Methods other than thermal decomposition may also be used to remove  615  sacrificial material  108 . By way of example, sacrificial material  108  may be removed by etching, dissolving, or other suitable method. It should be appreciated that the removal of sacrificial material  108  produces a waveguide  102  that may be used to conduct high frequency electrical signals, or other signals. This process may be less expensive than other traditional methods of waveguide construction.  
         [0020]     While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.