Chip-scale sensing device for low density material and method of making same

Abstract

An electrochemical sensor device that is efficiently and economically produced at the chip level for a variety of applications is disclosed. In some aspects, the device is made on or using a wafer technology whereby a sensor chamber is created by said wafer and a gas port allows for a working electrode of the sensor to detect certain gases. Large scale production is possible using wafer technology where individual sensors are produced from one or more common wafers. Integrated circuits are made in or on the wafers in an integrated way so that the wafers provide the substrate for the integrated circuitry and interconnects as well as providing the definition of the chambers in which the gas sensors are disposed.

What is claimed is: 
     
         1 . A chip-level electrochemical sensing device, comprising:
 a base wafer having externally- and internally-facing sides, said base wafer further having a plurality of through-vias penetrating said base wafer and extending between the internally- and externally-facing sides thereof;   a cap wafer disposed over the internally-facing side of said base wafer;   a sensor chamber at least partially defined by said internally-facing side of said base wafer and said cap wafer;   a gas port formed by a first of said plurality of through-vias, the gas port providing gas communication between said externally- and internally-facing sides of the base wafer to allow a gas on the externally-facing side of the base wafer to pass through said gas port into said sensor chamber;   an electrochemical sensor disposed in said sensor chamber, the electrochemical sensor responsive to a property of said gas and comprising:
 a working electrode exposed to said gas entering the sensor chamber through said gas port; 
 a second electrode; 
 a third electrode; 
 a solid electrolyte that couples the working electrode, the second electrode, and the third electrode; and 
 a gasket that defines first and second sub-chambers in the sensor chamber, the working electrode and the second electrode disposed in the first sub-chamber and the third electrode disposed in the second sub-chamber, the gasket at least partially gas-isolating the working and second electrodes from the third electrode; 
   a first conducting through-via electrically coupling said working electrode to a first electrical contact on the externally-facing side of said base wafer, the first conducting through-via comprising a second of said plurality of through-vias;   a second conducting through-via electrically coupling said second electrode to a second electrical contact on the externally-facing side of said base wafer, the second conducting through-via comprising a third of said plurality of through-vias;   a third conducting through-via electrically coupling said third electrode to a third electrical contact on the externally-facing side of said base wafer, the third conducting through-via comprising a fourth of said plurality of through-vias;   a plurality of electrical connections that carry electrical signals to and from said device; and   an integrated circuit constructed on or in the base wafer or the cap wafer, said integrated circuit electrically coupled to said plurality of electrical connections.   
     
     
         2 . The device of  claim 1 , wherein the gasket fully gas-isolates the working and second electrodes from the third electrode. 
     
     
         3 . The device of  claim 1 , wherein the gasket is cured from a liquid. 
     
     
         4 . The device of  claim 1 , wherein the second electrode comprises a counter electrode. 
     
     
         5 . The device of  claim 4 , wherein the third electrode comprises a reference electrode. 
     
     
         6 . The device of  claim 1 , wherein the gasket is a first gasket and the device further comprises a second gasket that defines a third sub-chamber in the sensor chamber, the second electrode disposed in the third sub-chamber, the second gasket at least partially gas-isolating the second electrode from the working electrode and/or the third electrode. 
     
     
         7 . The device of  claim 6 , wherein the second gasket fully gas-isolates the second electrode from the working electrode and/or the third electrode. 
     
     
         8 . The device of  claim 1 , wherein said sensor chamber is at least partially defined by a recess in the internally-facing side of said base wafer and/or in an internally-facing side of said cap wafer. 
     
     
         9 . The device of  claim 1 , wherein the working and second electrodes are disposed between said electrolyte and said internally-facing side of the base wafer. 
     
     
         10 . The device of  claim 1 , further comprising a gas-permeable filter disposed over the gas port to filter the gas passing through said gas port. 
     
     
         11 . The device of  claim 1 , wherein said sensor chamber is further defined by sidewalls that separate the base and cap wafers, the sidewalls comprising a spacer wafer having a thickness that separates the base and cap wafers. 
     
     
         12 . The device of  claim 1 , wherein:
 the electrochemical sensor further comprises a fourth electrode, and   the solid electrolyte couples the working electrode, the second electrode, the third electrode, and the fourth electrode.   
     
     
         13 . The device of  claim 12 , wherein the fourth electrode is disposed in the second sub-chamber whereby the gasket at least partially gas-isolates the working and second electrodes from the third and fourth electrodes. 
     
     
         14 . The device of  claim 12 , wherein:
 the gasket further defines a third sub-chamber in the sensor chamber, and   the fourth electrode is disposed in the third sub-chamber,   whereby the gasket at least partially gas-isolates (a) the working and second electrodes, (b) the third electrode, and (c) the fourth electrode from one another.   
     
     
         15 . A method for making a chip-level electrochemical sensor device, comprising:
 forming a sensor chamber between a base wafer and a cap wafer, the base wafer and the cap wafer each having an internally-facing side that at least partially defines the sensor chamber;   forming a working electrode, a second electrode, and a third electrode in the sensor chamber;   placing a solid electrolyte in the sensor chamber, the sold electrolyte in contact with said working electrode, said second electrode, and said third electrode;   depositing a liquid gasket material in the sensor chamber;   curing the liquid gasket material to form a solid gasket that defines first and second sub-chambers in the sensor chamber, the working electrode and second electrode disposed in the first sub-chamber and the third electrode disposed in the second sub-chamber, the solid gasket at least partially gas-isolating the working and second electrodes from the third electrode;   defining a gas port through-via in said base wafer or said cap wafer, the gas port via allowing movement of a gas from an exterior of said device to the first sub-chamber;   forming a first conducting through-via in said base wafer or said cap wafer, the first conducting through-via electrically coupled to said working electrode;   forming a second conducting through-via in said base wafer or said cap wafer, the second conducting through-via electrically coupled to said second electrode;   forming a third conducting through-via in said base wafer or said cap wafer, the third conducting through-via electrically coupled to said third electrode; and   forming electrical connections between the first, second, and third conducting through-vias and external connections points.   
     
     
         16 . The method of  claim 15 , wherein the solid gasket fully gas-isolates the working and second electrodes from the third electrode. 
     
     
         17 . The method of  claim 15 , wherein the second electrode comprises a counter electrode and the third electrode comprises a reference electrode. 
     
     
         18 . The method of  claim 15 , wherein the solid gasket defines a third sub-chamber in the sensor chamber, the second electrode disposed in the third sub-chamber. 
     
     
         19 . The method of  claim 15 , wherein said base wafer and/or said cap wafer comprise a silicon wafer. 
     
     
         20 . The method of  claim 15 , further comprising placing a spacer wafer between the base and cap wafers to form sidewalls of the sensor chamber. 
     
     
         21 . The method of  claim 15 , further comprising:
 forming a fourth electrode in the sensor chamber; and   placing the solid electrolyte in contact with said fourth electrode.   
     
     
         22 . The method of  claim 21 , further comprising placing the fourth electrode in the second sub-chamber whereby the solid gasket at least partially gas-isolates the working and second electrodes from the third and fourth electrodes. 
     
     
         23 . The method of  claim 22 , wherein the solid gasket further defines a third sub-chamber in the sensor chamber, and the method further comprises placing the fourth electrode in the third sub-chamber, whereby the solid gasket at least partially gas-isolates (a) the working and second electrodes, (b) the third electrode, and (c) the fourth electrode from one another.