Gas Sensor with a Gas Permeable Region

Abstract

In an embodiment a method includes forming a dielectric membrane on a semiconductor substrate comprising a bulk-etched cavity portion, forming a heater within or over the dielectric membrane, forming a material for sensing a gas on a side of the dielectric membrane, forming a support structure near the material, wherein the support structure comprises an inorganic material and forming a gas permeable region coupled to the support structure in order to protect the material.

What is claimed is: 
     
         1 . A method for manufacturing a gas sensing device, the method comprising:
 forming a dielectric membrane on a semiconductor substrate comprising a bulk-etched cavity portion;   forming a heater within or over the dielectric membrane;   forming a material for sensing a gas on a side of the dielectric membrane;   forming a support structure near the material, wherein the support structure comprises an inorganic material; and   forming a gas permeable region coupled to the support structure in order to protect the material.   
     
     
         2 . The method according to  claim 1 , wherein the support structure is attached by wafer bonding. 
     
     
         3 . The method according to  claim 1 , wherein a gas permeable layer is attached to the support structure, before the support structure is attached by wafer bonding. 
     
     
         4 . The method according to  claim 1 , wherein forming the dielectric membrane comprises forming the dielectric membrane such that it is supported along its entire perimeter by the semiconductor substrate. 
     
     
         5 . The method according to  claim 1 , wherein forming the dielectric membrane comprises using an etching technique to back-etch the semiconductor substrate to form the bulk-etched cavity portion. 
     
     
         6 . The method according to  claim 5 , wherein the etching technique is selected from the group consisting of deep reactive ion etching (DRIE), anisotropic or crystallographic wet etching, potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAH). 
     
     
         7 . The device manufactured according to  claim 1 , wherein the support structure comprises a semiconductor material. 
     
     
         8 . The method according to  claim 1 , wherein the support structure comprises a material comprising a glass or a ceramic. 
     
     
         9 . The method according to  claim 1 , wherein the semiconductor substrate forms the support structure. 
     
     
         10 . The method according to  claim 1 , wherein the dielectric membrane is only supported by one or more dielectric beams to connect the dielectric membrane to the semiconductor substrate. 
     
     
         11 . The method according to  claim 1 , wherein the material is a gas sensing material. 
     
     
         12 . The method according to  claim 11 , wherein the gas sensing material comprises a metal oxide material or a combination of metal oxides. 
     
     
         13 . The method according to  claim 1 , wherein the material is deposited as a gate electrode, or is electrically connected to the gate electrode of a field effect transistor (FET). 
     
     
         14 . The method according to  claim 1 , wherein the dielectric membrane is formed using an etching technique for back-etching the semiconductor substrate, the etching technique being selected from the group consisting of deep reactive ion etching (DRIE), anisotropic or crystallographic wet etching, potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAH). 
     
     
         15 . The method according to  claim 1 , wherein the dielectric membrane is formed by a front side etch of the semiconductor substrate. 
     
     
         16 . The method according to  claim 1 , wherein the heater is a resistive heater comprising a CMOS material comprising aluminium, copper, titanium, molybdenum, polysilicon, single crystal silicon tungsten, or titanium nitride. 
     
     
         17 . The method according to  claim 1 , wherein the semiconductor substrate is a bulk silicon substrate or an SOI substrate.