Capacitive sensor integrated onto semiconductor circuit

A gas sensor comprising:

• a semiconductor circuit having a top passivation layer;
• a metal bottom electrode on the top passivation layer of the semiconductor circuit, wherein said metal bottom electrode is located over an area of the semiconductor circuit that contains active circuitry,
• a metal landing pad on the passivation layer and electrically separate from the metal bottom electrode;
• a gas sensitive layer on the metal bottom electrode and the metal landing pad, the gas sensitive layer including a via hole exposing a portion of the metal landing pad;
• a porous top electrode on the gas sensitive layer, wherein an area formed by the porous top electrode completely overlays an area formed by the metal bottom electrode, and wherein the porous top electrode is electrically connected to the metal landing pad through the via hole in the gas sensitive layer;
• and
• a first metal trace between the metal bottom electrode and a first bond pad and a second metal trace between the metal landing pad and a second bond pad;
• wherein the semiconductor circuit measures a capacitance of the gas sensitive layer by applying a signal to the metal bottom electrode and measuring a charge displaced by the capacitance through the porous top electrode.

A gas sensor comprising:

• an integrated circuit capable of measuring capacitance of a parallel plate capacitive sensor by applying a voltage and measuring a resulting displaced charge, and having a top passivation layer;
• a metal layer formed directly onto a top outer surface of the passivation layer of the integrated circuit and located over a surface area of the integrated circuit that contains active circuitry, the metal layer defining a bottom electrode of a parallel plate capacitor, a landing pad for connection of a top electrode of the parallel plate capacitor, and a first trace connecting the bottom electrode to a first bond pad and a second trace connecting the landing pad to a second bond pad, the first and second bond pads being separately connected to the integrated circuit;
• a gas sensitive dielectric layer covering exposed portions of the passivation layer and the metal layer, the gas sensitive dielectric layer having defined therethrough a via to the landing pad;
• and
• a porous top electrode on the gas sensitive dielectric layer and completely covering an area of the bottom electrode defined in the metal layer and filling the via in the gas sensitive dielectric layer to make electrical connection to the landing pad;
• the integrated circuit being configured to output a signal indicative of a concentration of a gas responsive to determined capacitance of the gas sensitive dielectric layer.