Wafer-level hermetic micro-device packages

Abstract

A hermetically sealed micro-device package encapsulating a micro-device and including a transparent window allowing light to pass into and out of a cavity containing the micro-device comprises a semiconductor substrate having a micro-device operably disposed thereupon. The substrate has a first frame-attachment area formed thereupon having a plan that circumscribes the micro-device. A sheet of transparent material has a window aperture portion defined thereupon, the sheet having a second frame-attachment area formed thereupon having a plan that circumscribes the window aperture portion. A frame/spacer is positioned between, and hermetically bonded to, the semiconductor substrate and the transparent sheet, the frame/spacer including a continuous sidewall having a plan on one side substantially corresponding to, and substantially in register with, the plan of the first frame-attachment area, having a plan on the opposite side substantially corresponding to, and substantially in register with, the plan of the second frame-attachment area, and having a height that exceeds the height of the micro-device.

1 . A hermetically sealed micro-device package encapsulating a micro-device and including a transparent window allowing light to pass into and out of a cavity containing the micro device, comprising: 
 a semiconductor substrate having a micro-device operably disposed thereupon, the substrate having a first frame-attachment area formed thereupon having a plan that circumscribes the micro-device;    a sheet of transparent material having a window aperture portion defined thereupon, the sheet having a second frame-attachment area formed thereupon having a plan that circumscribes the window aperture portion; and    a frame/spacer positioned between, and hermetically bonded to, the semiconductor substrate and the transparent sheet, the frame including a continuous sidewall having a plan on one side substantially corresponding to, and substantially in register with, the plan of tie fit frame-attachment area, having a plan on the opposite side substantially corresponding to, and substantially in register with, the plan of the second frame-attachment area, and having a height that exceeds the height of the micro-device.    
     
     
         2 . A package in accordance with  claim 1 , wherein the semiconductor substrate is substantially formed of silicon (Si).  
     
     
         3 . A package in accordance with  claim 1 , wherein the semiconductor substrate is substantially formed of gallium arsenide (GaAs).  
     
     
         4 . A package in accordance with  claim 1 , wherein the frame is formed of a material having a CTE substantially matched to the CTE of the transparent sheet and to the CTE of the semiconductor substrate.  
     
     
         5 . A package in accordance with  claim 1 , wherein at least one of the hermetic bond between the frame and the semiconductor substrate and the hermetic bond between the frame and the transparent sheet is formed by diffusion bonding.  
     
     
         6 . A package in accordance with  claim 5 , wherein both the hermetic bond between the frame and the semiconductor substrate and the hermetic bond between the frame and the transparent sheet are formed by diffusion bonding.  
     
     
         7 . A package in accordance with  claim 6 , wherein the hermetic diffusion bond between the frame and the semiconductor substrate and the hermetic diffusion bond between the frame and the transparent sheet are formed in accordance with the following steps: 
 pressing the substrate and the sheet against the frame with sufficient force to produce a first predetermined contact pressure along a first junction region between the frame and the first frame-attachment area of the substrate and a second predetermined contact pressure along a second junction region between the frame and the second frame-attachment area of the sheet;    heating the first junction region to produce a first predetermined temperature along the first junction region;    heating the second junction region to produce a second predetermined temperature along the second junction region;    maintaining the first predetermined contact pressure and the first predetermined temperature until a diffusion bond is formed between the frame and the substrate all along the first junction region; and    maintaining the second predetermined contact pressure and the second predetermined temperature until a diffusion bond is formed between the frame and sheet all along the second junction region.    
     
     
         8 . A package in accordance with  claim 5 , wherein during bonding of the frame to the semiconductor substrate and during bonding of the frame to the transparent sheet, the temperature of the window aperture portion of the sheet remains below the glass transition temperature (T G ) of the transparent material.  
     
     
         9 . A multi-package assembly including a plurality of hermetically sealed cavities hermetically separated from one another by frame sidewalls, each of the cavities containing a micro-device positioned below a transparent window aperture allowing light to pass into and out of the cavity, the assembly comprising: 
 a unitary semiconductor substrate having a plurality of micro-devices operably disposed thereupon, the substrate having a first frame-attachment area formed thereupon having a plan that circumscribes each of the micro-devices;    a unitary sheet of transparent material, the sheet having a second frame-attachment area from thereupon having a plan that circumscribes a plurality of transparent window aperture positions of the sheet;    a frame including a plurality of sidewalls, the sidewalls collectively having a plan on one side of the frame that substantially corresponds to, and is substantially in register with, the plan of the first frame-attachment area, having a plan on the opposite side of the frame that substantially corresponds to, and is substantially in register with, the plan of the second frame-attachment area, and having a height that exceeds the height of the micro-devices as disposed on the substrate;    wherein the semiconductor substrate, frame and transparent sheet are hermetically bonded together along the first and second frame attachment areas to form a plurality of hermetically sealed cavities separated from one another by the frame sidewalls, each of the cavities containing a micro-device positioned below one of the window aperture portions of the sheet.    
     
     
         10 . A multi-package assembly in accordance with  claim 9 , wherein the semiconductor substrate is substantially formed of silicon (Si).  
     
     
         11 . A multi-package assembly in accordance with  claim 9 , wherein the semiconductor substrate is substantially formed of gallium arsenide (GaAs).  
     
     
         12 . A multi-package assembly in accordance with  claim 9 , wherein at least one of the hermetic bond between the frame and the semiconductor substrate and the hermetic bond between the frame and the transparent sheet is formed by diffusion bonding.  
     
     
         13 . A multi-package assembly in accordance with  claim 12 , wherein both the hermetic bond between the frame and the semiconductor substrate and the hermetic bond between the frame and the transparent sheet are formed by diffusion bonding.  
     
     
         14 . A multi-package assembly in accordance with  claim 13 , wherein the hermetic diffusion bond between the frame and the semiconductor substrate and the hermetic diffusion bond between the frame and the transparent sheet frame formed in accordance with the following steps:. 
 pressing the substrate and the sheet against the frame with sufficient force to produce a first predetermined contact pressure along a first junction region between the frame and the first frame-attachment area of the substrate and a second predetermined contact pressure along a second junction region between the frame and the second frame-attachment area of the sheet;    heating the first junction region to produce a first predetermined temperature along the first junction region;    heating the second junction region to produce a second predetermined temperature along the second junction region;    maintaining the first predetermined contact pressure and the first predetermined temperature until a diffusion bond is formed between the frame and the substrate all along the first junction region; and    maintaining the second predetermined contact pressure and the second predetermined temperature until a diffusion bond is formed between the frame and sheet all along the second junction region.    
     
     
         15 . A multi-package assembly in accordance with  claim 9 , wherein cutting through selected sidewalls will divide the assembly into discrete sub-assemblies, each of the discrete sub-assemblies including at least one hermetically sealed package containing a micro-device positioned below a transparent window aperture.  
     
     
         16 . A multi-package assembly in accordance with  claim 15 , wherein at least some of the sidewalls of the frame are grooved to a reduced thickness at locations between adjacent cavities, thereby facilitating subsequent cutting through of the grooved sidewalls to divide the assembly.  
     
     
         17 . A hermetically sealed micro-device package encapsulating a micro-device and including a transparent window allowing light to pass into and out of a cavity containing the micro-device, the package being formed by dividing a multi-package assembly in accordance with  claim 9  into smaller sub-assemblies.