Hermetically Sealed Implant Sensors With Vertical Stacking Architecture

Abstract

The present invention describes vertically stacked and hermetically sealed implantable pressure sensor devices for measuring a physiological signal. The implantable device comprises multiple layers, including a first wafer having a pressure sensor configured to measure the physiological signal and a second wafer having at least a digitizing integrated circuit. The first wafer is vertically stacked or disposed over the second wafer so as to form a hermetic seal. The device may include one or more additional layers adapted for energy storage and transfer, such as a third layer having a super-capacitor and a fourth layer having a thin film battery.

What is claimed is: 
     
         1 . A vertically stacked and hermetically sealed implantable pressure sensor device for measuring a physiological signal, the implantable device comprising:
 a first wafer comprising at least a pressure sensor configured to measure the physiological signal; and   a second wafer comprising at least a digitizing integrated circuit, wherein the first wafer is vertically stacked or disposed over the second wafer so as to form a hermetic seal.   
     
     
         2 . The implantable device of  claim 1 , wherein the vertical stacking of the wafers is configured to create a hermetically sealed cavity between the first and second wafers. 
     
     
         3 . The implantable device of  claim 1 , wherein the implantable device comprises a size or shape capable of implantation through an injector or syringe having a gauge of 19 or higher. 
     
     
         4 . The implantable device of  claim 1 , wherein the physiological signal comprises an intraocular pressure, an intracranial pressure, or a cardiovascular pressure. 
     
     
         5 . The implantable device of  claim 4 , wherein the implantable device is sized or shaped to be positionable within a vitreous body of an eye so as to measure an intraocular pressure of a vitreous humour. 
     
     
         6 . The implantable device of  claim 1 , wherein the pressure sensor comprises a capacitive pressure transducer, wherein the capacitive pressure transducer comprises at least a first cavity structure having a membrane, wherein the first cavity is under vacuum such that the physiological signal comprises a pressure measurement. 
     
     
         7 . The implantable device of  claim 6 , wherein the capacitive pressure transducer further comprises at least a second cavity structure having a membrane, wherein the second cavity is under vacuum and the membrane has a stiffness higher than that of the first cavity structure so as to be less sensitive to pressure such that a signal obtained from the second cavity comprises a reference measurement for comparison with the pressure measurement. 
     
     
         8 . The implantable device of  claim 1 , wherein the second wafer further comprises any of radio frequency link, power storage, and data storage 
     
     
         9 . The implantable device of  claim 1 , wherein each wafer comprises a maximum thickness of about 200 microns or less. 
     
     
         10 . The implantable device of  claim 1 , wherein each wafer has substantially the same thickness. 
     
     
         11 . The implantable device of  claim 1 , wherein the first wafer has a greater thickness than the second wafer. 
     
     
         12 . The implantable device of  claim 1 , wherein the implantable device comprises a maximum thickness of about 200 microns or less, a maximum length of about 4 mm or less, and a width of 650 microns or less. 
     
     
         13 . The implantable device of  claim 1 , wherein the first and second wafers are formed from substrate materials having matched temperature coefficients of expansion or wherein the first and second wafers comprise the same material. 
     
     
         14 . The implantable device of  claim 1 , further comprising at least one stress isolation feature incorporated into the first wafer to mechanically decouple the pressure sensor from the second wafer. 
     
     
         15 . The implantable device of  claim 1 , further comprising a sealing ring disposed between the first and second wafers configured to hermetically seal the first and second wafers. 
     
     
         16 . The implantable device of  claim 15 , further comprising a dielectric layer disposed over the implantable device to electrically isolate and encapsulate the first and second wafer and provide an adhesion layer. 
     
     
         17 . The implantable device of  claim 16 , further comprising a titanium barrier disposed over the dielectric layer so as to further hermetically encapsulate the first and second wafers, further comprising a biocompatible polymer coating disposed over the titanium barrier. 
     
     
         18 . The implantable device of  claim 1 , wherein all electrical connections are located on a bottom or back side of the first and second wafers so as to provide an interface to a media which is isolated from any electrical connection. 
     
     
         19 . The implantable device of  claim 1 , further comprising a third wafer having a capacitor, wherein the second wafer is vertically stacked or disposed over the third wafer. 
     
     
         20 . The implantable device of  claim 1 , further comprising a fourth wafer having a thin-film battery, wherein the third wafer is vertically stacked or disposed over the fourth wafer.