Anodically Bonded Cell, Method for Making Same and Systems Incorporating Same

Abstract

A cell suitable for use with an atomic clock and a method for making the same, the cell including: a silicon wafer having a recess formed therein; at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon sealing the recess; and, an alkali metal containing component and buffer gas contained in the recess. The method includes: providing a silicon wafer; forming a cavity through the silicon wafer; introducing an alkali metal containing component and buffer gas into the cavity; and, anodically bonding at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to the wafer to close the cavity.

1 . A cell suitable for use with an atomic clock comprising:
 a silicon wafer having a recess formed therein;   an alkali metal containing component and buffer gas in said recess; and,   at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon closing said recess.   
   
   
       2 . The cell of  claim 1 , further comprising at least a second amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon sealing said recess. 
   
   
       3 . The cell of  claim 1 , wherein said amorphous silicate member comprises borosilicate glass. 
   
   
       4 . The cell of  claim 1 , wherein said alkali metal component comprises a Cs vapor. 
   
   
       5 . The cell of  claim 4 , wherein said buffer gas comprises at least one of argon, neon and nitrogen. 
   
   
       6 . The cell of  claim 1 , further comprising at least one heater positioned substantially adjacent to said at least one amorphous silicate member. 
   
   
       7 . The cell of  claim 6 , wherein said heater comprises a patterned indium tin oxide heater. 
   
   
       8 . The cell of  claim 1 , further comprising a photo detector being integrated with said silicon wafer. 
   
   
       9 . The cell of  claim 1 , further comprising a laser suitable for emitting optical energy having a center wavelength of about 894 nm into said cavity. 
   
   
       10 . The cell of  claim 9 , further comprising at least one wave plate between said laser and said alkali metal containing component. 
   
   
       11 . The cell of  claim 9 , further comprising an amplitude modulator positioned between said laser and said alkali metal containing component. 
   
   
       12 . The cell of  claim 9 , further comprising a neutral density filter positioned between said laser and said alkali metal containing component. 
   
   
       13 . The cell of  claim 9 , further comprising a reflector positioned with respect to said cavity to reflect emissions from said laser back through said cavity. 
   
   
       14 . A process for fabricating a cell suitable for use with an atomic clock comprising:
 providing a silicon wafer;   forming a cavity through said silicon wafer;   introducing an alkali metal containing component and buffer gas into said cavity; and,   anodically bonding at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to said wafer.   
   
   
       15 . The process of  claim 14 , wherein said introducing is prior to bonding at least one of said members to said wafer. 
   
   
       16 . The process of  claim 14 , wherein said introducing comprises forming an aperture through one of said members. 
   
   
       17 . The process of  claim 16 , wherein said introducing further comprises flowing an alkali metal atomic stream through said aperture. 
   
   
       18 . The process of  claim 16 , wherein said aperture is between about 100 micrometers and about 125 micrometers in diameter. 
   
   
       19 . The process of  claim 16 , wherein said aperture is at an angle of about 60 degrees to a surface plane of said cell. 
   
   
       20 . The process of  claim 14 , wherein said amorphous silicate member comprises borosilicate glass. 
   
   
       21 . The process of  claim 14 , further comprising anodically bonding a second amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to said wafer to close said cavity. 
   
   
       22 . The process of  claim 14 , wherein said alkali metal containing component comprises Cs. 
   
   
       23 . The process of  claim 22 , wherein said buffer gas comprises at least one of argon, neon and nitrogen. 
   
   
       24 . The process of  claim 13 , wherein said buffer gas consists essentially of about 79% argon and about 21% nitrogen. 
   
   
       25 . The process of  claim 22 , wherein said introducing comprises providing Cs salt and a reducing agent. 
   
   
       26 . The process of  claim 14 , wherein said introducing comprises providing liquid cesium near a periphery of said cavity. 
   
   
       27 . The process of  claim 14 , wherein said introducing comprises a liquid Cs pin transfer. 
   
   
       28 . The process of  claim 14 , further comprising providing a protectant within said cavity. 
   
   
       29 . The process of  claim 28 , wherein said providing a protectant comprises depositing at least one of SiO 2 , Al 2 O 3  or Si x N y . 
   
   
       30 . The process of  claim 14 , wherein said forming comprises at least one of:
 providing an etch mask over said silicon wafer and caustic etching said silicon wafer dependently upon said etch mask; and,   physical eroding of said silicon wafer.   
   
   
       31 . The process of  claim 14 , further comprising forming a second cavity in said silicon wafer and in physical communication with said first cavity. 
   
   
       32 . A cell suitable for use with an atomic clock comprising:
 a first amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon and a recess;   an alkali containing component and buffer gas in said recess;   a silicon containing layer over said first borosilicate glass member and around a periphery of said recess; and,   a second amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon and being anodically bonded to said silicon containing layer and closing said recess.   
   
   
       33 . The cell of  claim 32 , wherein said alkali metal component comprises a Cs vapor and said buffer gas comprises at least one of argon, neon and nitrogen. 
   
   
       34 . The cell of  claim 31 , further comprising at least one heater positioned substantially adjacent to at least one of said borosilicate glass members. 
   
   
       35 . The cell of  claim 21 , further comprising at least one of SiO 2  and Al 2 O 3  coating at least a portion of an interior surface of said recess. 
   
   
       36 . A process for fabricating a cell suitable for use with an atomic clock comprising:
 providing a first amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon and a recess;   providing a silicon containing layer over said first member and around a periphery of said recess;   introducing an alkali containing component and buffer gas into said recess; and,   anodically bonding a second amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon to said silicon containing layer to close said recess.   
   
   
       37 . The process of  claim 36 , wherein said component comprises Cs and said buffer gas comprises at least one of argon, neon and nitrogen. 
   
   
       38 . The process of  claim 36 , wherein said introducing comprises a liquid Cs pin transfer. 
   
   
       39 . The process of  claim 36 , wherein said introducing is prior to said closing said recess. 
   
   
       40 . A system comprising:
 a clock comprising a silicon wafer having a recess formed therein; at least one amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon closing said recess; and, an alkali metal containing component and buffer gas contained in said recess; and,   a device having an input coupled to said clock and being operatively responsive to said input.   
   
   
       41 . The system of  claim 40 , wherein said device comprises at least one of a distributed computing system nodal computing element, a global positioning system signal receiver and a communications transceiver. 
   
   
       42 . A system comprising:
 a clock comprising a first amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon and a recess; an alkali containing component and buffer gas in said recess; a silicon containing layer over said first borosilicate glass member and around said recess; and, a second amorphous silicate member having an ion mobility and temperature expansion coefficient approximately that of silicon anodically bonded to said silicon containing layer and closing said recess; and,   a device having an input coupled to said clock and being operatively responsive to said input.   
   
   
       43 . The system of  claim 42 , wherein said device comprises at least one of a distributed computing system nodal computing element, a global positioning system signal receiver and a communications transceiver. 
   
   
       44 . A system suitable for use with an atomic clock comprising:
 a cell defining a cavity having an interior volume of less than about 1 microliter; and,   an atomic vapor and buffer gas in said cavity and at a pressure greater than about an atmosphere.