Detection of sensor passivation failure
Embodiments described herein involve a test structure for a sensor, comprising a substrate being part of the sensor and a moat structure disposed on the substrate. The sensor comprises a resonating structure comprising a piezoelectric layer having an active region. A passivation layer overlays the resonating structure including the active region. The moat structure is configured to at least partially surround the active region in plan view. An electrode is disposed on the substrate and comprises an electrode path. The electrode path crosses the moat structure at least one time in plan view. The moat structure at each moat crossing is configured to cause a change in electrical resistance of the electrode if there is passivation failure of the passivation layer at the moat crossing.
1 . A test structure for a sensor, comprising:
a substrate being part of the sensor, the sensor comprising a resonating structure comprising a piezoelectric layer having an active region, the sensor further comprising a passivation layer overlaying the resonating structure including the active region;
a moat structure disposed on the substrate and configured to at least partially surround the active region of the resonating structure in plan view;
an electrode disposed on the substrate and comprising an electrode path configured to cross the moat structure a plurality of times along a majority of the moat structure in plan view, wherein the moat structure at each moat crossing is configured to cause a change in electrical resistance of the electrode if there is passivation failure of the passivation layer at the moat crossing;
a detector configured to detect the change in electrical resistance of the electrode; and
an analyzer configured to determine passivation failure of the passivation layer based on the detected change in electrical resistance.
2 . The test structure of claim 1 , wherein the change is resistance comprises an increase in resistance.
3 . The test structure of claim 1 , wherein the moat structure is substantially a circular structure.
4 . The test structure of claim 1 , wherein the electrode path is configured to cross the moat structure in a range of about 10 times to about 30 times.
5 . The test structure of claim 1 , wherein the electrode path is configured to cross the moat structure about 12 times.
6 . The test structure of claim 1 , wherein the electrode path is configured to cross the moat structure about 24 times.
7 . The test structure of claim 1 , further comprising an analyzer configured to determine if the change in resistance is in a predetermined threshold range.
8 . The test structure of claim 7 , wherein the predetermined threshold range is about 35Ω to about 95Ω.
9 . The test structure of claim 8 , wherein the predetermined threshold range is about 50Ω to about 80Ω.
10 . The test structure of claim 7 , wherein if it is determined that the change in resistance is outside of the predetermined threshold range, the analyzer is configured to determine that passivation failure has occurred.
11 . A system, comprising:
a sensor comprising:
a substrate;
a resonating structure disposed proximate the substrate and comprising at least one piezoelectric layer, the resonating structure having an active region and a passivation layer overlying the resonating structure including the active region;
a moat structure at least partially surrounding the active region of the resonating structure in plan view;
an electrode comprising an electrode path configured to cross the moat structure a plurality of times along a majority of the moat structure in plan view, wherein the moat structure at each moat crossing is configured to cause a change in electrical resistance of the electrode if there is passivation failure of the passivation layer at the moat crossing;
a detector configured to detect the change in electrical resistance; and
an analyzer configured to determine passivation failure of the passivation layer based on the change in electrical resistance.
12 . The system of claim 11 , wherein the change is resistance comprises an increase in resistance.
13 . The system of claim 11 , wherein the moat structure is substantially a circular structure.
14 . The system of claim 11 , wherein the electrode path is configured to cross the moat structure about 12 times.
15 . The system of claim 11 , wherein the electrode path is configured to cross the moat structure about 24 times.
16 . The system of claim 11 , wherein the analyzer is configured to determine if the detected change in resistance is in a predetermined threshold range.
17 . The system of claim 16 , wherein the predetermined threshold range is about 35Ω to about 95Ω.
18 . The system of claim 17 , wherein the predetermined threshold range is about 50Ω to about 80Ω.