Method for fabrication of a sensor device

A method for fabrication of a sensor device, the sensor device being adapted for measuring a first parameter of a test substance, the method comprising the steps of:

• i) providing a substrate with a front side and a back side, the front and back sides each extending in an in-plane direction and being located at a distance to one another in an out-of-plane direction;
• ii) depositing from the front side of the substrate a structured first protection layer;
• iii) arranging on the front side of the substrate a stack of dielectric and conducting in-plane layers, the stack comprising:
• a first electrode;
• a second electrode;
• a sacrificial layer;
• wherein the first and second electrodes are arranged on the first protection layer and at a distance to one another in the in-plane direction,
• wherein the sacrificial layer is arranged without overlap with the first protection layer with respect to the in-plane direction and between the first electrode and the second electrode with respect to the in-plane direction;
• and the stack further comprising:
• a passivation layer that covers front sides of the first and second electrodes and the sacrificial layer, respectively;
• and
• iv) generating from the back side of the substrate, in a process step an opening, the opening extending through the substrate from its back side to its front side and the opening removing at least part of the sacrificial layer, thereby creating a sensing cavity extending between the first electrode and the second electrode, wherein the first protection layer protects the first and second electrodes from being removed during the process step iv).

A sensor device for measuring a first parameter of a test substance, the sensor device comprising:

• a substrate, having a first side and a second side, the first and second sides each extending in an in-plane direction and being located at a distance to one another in an out-of-plane direction, the substrate having an opening extending from the second side to the first side of the substrate;
• a stack arranged on the first side of the substrate and at least partly spanning the opening;
• a first electrode and a second electrode arranged in the stack such as to overlap with the opening with respect to the in-plane direction, the first electrode and the second electrode being separated in the in-plane direction by a space from one another;
• wherein the opening is further extending at least partly into the space between the first electrode and the second electrode, thereby delimiting a sensing cavity therebetween;
• wherein the first and second electrodes are made from standard CMOS polysilicon layer materials.

A sensor device for measuring a first parameter of a test substance, the sensor device comprising:

• a substrate, having a first side and a second side, the first and second sides each extending in an in-plane direction and being located at a distance to one another in an out-of-plane direction, the substrate having an opening extending from the second side to the first side of the substrate;
• a stack arranged on the first side of the substrate and at least partly spanning the opening;
• a first electrode and a second electrode arranged in the stack such as to overlap with the opening with respect to the in-plane direction, the first electrode and the second electrode being separated in the in-plane direction by a space from one another;
• wherein the opening is further extending at least partly into the space between the first electrode and the second electrode, thereby delimiting a sensing cavity therebetween;
• wherein the first and second electrodes are made from standard CMOS polysilicon layer materials, wherein a structured first protection layer is arranged on second sides of the first and second electrodes, the structured first protection layer being adapted to protect the first and second electrodes from being damaged during the etching process that forms the sensing cavity.