Integrated device of a capacitive type for detecting humidity, in particular manufactured using a CMOS technology
An integrated capacitive-type humidity sensor formed in a semiconductor chip integrating a sensing capacitor and a reference capacitor. Each of the sensing and reference capacitors have at least a first electrode and at least a second electrode, the first and second electrodes of each of the sensing and reference capacitors being arranged at distance and mutually insulated. A hygroscopic layer extends on the sensing and reference capacitors and a conductive shielding region extends on the reference capacitor but not on the sensing capacitor.
1. A humidity sensor, comprising:
a semiconductor chip;
a sensing capacitor and a reference capacitor integrated in the semiconductor chip, each of the sensing and reference capacitors having a first electrode and a second electrode, the first and second electrodes of each of the sensing and reference capacitors being arranged at a distance from each other and mutually insulated;
a hygroscopic layer over the sensing and reference capacitors; and
a conductive shielding region over the reference capacitor and between the hygroscopic layer and the reference capacitor and not over the sensing capacitor.
2. The sensor according to claim 1 , wherein the hygroscopic layer is located over the conductive shielding region in a reference capacitor area of the chip that includes the reference capacitor.
3. The sensor according to claim 1 , wherein the semiconductor chip comprises an insulating structure that includes a plurality of metal regions arranged in a plurality of metal levels, the first and second electrodes of the sensing and reference capacitors being formed by respective metal regions.
4. The sensor according to claim 3 , wherein the plurality of metal levels includes an upper metal level, the first and second electrodes of the sensing and reference capacitors are formed in the upper metal level.
5. A semiconductor chip;
a sensing capacitor and a reference capacitor integrated in the semiconductor chip, each of the sensing and reference capacitors having a first electrode and a second electrode, the first and second electrodes of each of the sensing and reference capacitors being arranged at a distance from each other and mutually insulated;
a hygroscopic layer over the sensing and reference capacitors;
a conductive shielding layer over the reference capacitor and not over the sensing capacitor;
an insulating structure that includes a plurality of metal regions arranged in a plurality of metal levels, the first and second electrodes of the sensing and reference capacitors being formed by respective metal regions; and
a passivation layer over the conductive shielding layer, the conductive shielding layer and passivation layer having an opening over the sensing capacitor.
6. The sensor according to claim 3 , wherein the sensing and reference capacitors each comprise a plurality of first and second electrodes, the first electrodes of the sensing capacitor being coupled together by a first line, the second electrodes of the sensing capacitor being coupled together by a second line, the first electrodes of the reference capacitor being coupled together by a third line, the second electrodes of the reference capacitor being coupled together by a fourth line, and the first electrodes and second electrodes of the respective sensing and reference capacitors being interdigitated.
7. The sensor according to claim 1 , wherein the first and second electrodes of the sensing and reference capacitors have the same structure and shape as each other, and the sensing and reference capacitors extend laterally and at a distance to each other.
8. The sensor according to claim 1 , wherein the hygroscopic layer is one of a polymeric material and a low-K dielectric material.
9. The sensor according to claim 8 wherein the hygroscopic layer is polyimide.
10. The sensor according to claim 1 , comprising:
a capacitor bridge including the sensing and reference capacitors;
an operational amplifier having an input coupled to the capacitor bridge; and
an output generating an output signal indicative of humidity.
11. An apparatus comprising:
a humidity sensor that includes:
a semiconductor chip;
a sensing capacitor and a reference capacitor in the semiconductor chip, each of the sensing and reference capacitors having first electrodes and second electrodes, the first and second electrodes of each of the sensing and reference capacitors being arranged at a distance from each other;
a hygroscopic layer over the sensing and reference capacitors;
a conductive shielding region over the reference capacitor, the conductive shielding region not being over the sensing capacitor; and
a dielectric layer over the conductive shielding region but not over the sensing capacitor.
12. The apparatus according to claim 11 , wherein the apparatus is one of a weather station, a HVAC, a respiratory equipment, a humidifier, a gas sensor, a condensation level monitoring apparatus, and an air density monitoring apparatus.
13. The apparatus according to claim 11 , wherein the hygroscopic layer is a polymeric material.
14. The apparatus according to claim 11 , wherein the hygroscopic layer is located over the conductive shielding region in a reference capacitor area of the chip that includes the reference capacitor.
15. A process for manufacturing a humidity sensor, the process comprising:
forming a sensing capacitor and a reference capacitor in a semiconductor body, wherein forming the sensing and the reference capacitors comprises forming, for each of the sensing and reference capacitors, a first electrode and a second electrode, the first and second electrodes being arranged at a distance from each other and mutually insulated;
forming a hygroscopic layer on the sensing and reference capacitors, wherein forming a conductive shielding region comprises:
forming, on the insulating structure, a conductive shielding layer;
forming a passivation layer on the conductive shielding layer; and
removing the passivation layer and the conductive shielding layer from above the sensing capacitor; and
forming a conductive shielding region on the reference capacitor and not forming the conductive shielding region on the sensing capacitor.
16. The process according to claim 15 , wherein forming the sensing capacitor and the reference capacitor comprises:
forming an insulating structure; and
forming a plurality of metal regions arranged in a plurality of metal levels that includes an upper metal layer, wherein the first and second electrodes of the sensing and reference capacitors are formed by respective metal regions in the upper metal layer.
17. The process according to claim 15 , further comprising:
patterning the conductive shielding layer to form the conductive shielding region on the reference capacitor and at least one pad in a pad area of the body;
removing the passivation layer over the least one pad; and
removing the hygroscopic layer from the pad area.
18. The sensor according to claim 5 , wherein the first and second electrodes of the sensing and reference capacitors have the same structure and shape as each other, and the sensing and reference capacitors extend laterally and at a distance to each other.
19. The sensor according to claim 5 , wherein the hygroscopic layer is one of a polymeric material and a low-K dielectric material.
20. The sensor according to claim 5 , comprising:
a capacitor bridge including the sensing and reference capacitors;
an operational amplifier having an input coupled to the capacitor bridge; and
an output generating an output signal indicative of humidity.