Patent ID: 7710128

Claim:
A method for forming a capacitive humidity sensor, comprising: providing a substrate; depositing a first dielectric layer on said substrate; depositing a second dielectric layer on said first dielectric layer; and forming a first and a second series connected active humidity capacitor stacked on said second dielectric layer, said first and said second active humidity capacitors comprising: a first bottom and a second bottom sensing capacitor electrode separated from one another by a gap, a humidity sensing medium on said first and second bottom sensing capacitor electrodes, a top sensing capacitor electrode on said humidity sensing medium positioned over said first bottom and said second bottom sensing capacitor electrodes, wherein said top sensing capacitor electrode comprises a porous layer for allowing humidity to reach said humidity sensing medium, and a first bond pad coupled to said first bottom sensing capacitor electrode and a second bond pad coupled to said second bottom sensing capacitor electrode; wherein a first and a second series connected parasitic capacitor stacked below said first and said second series connected active humidity capacitor is provided comprising (i) top plates comprising said first bottom and said second bottom sensing capacitor electrodes, (ii) a dielectric comprising said second dielectric layer on said first dielectric layer, and (iii) bottom plates comprising said substrate, and wherein said first and second parasitic capacitors control a total capacitance of said capacitive humidity sensor to obtain a desired value for sensitivity of said capacitive humidity sensor without increasing its size.