[mems-talk] dramatic change in resistance of tungsten-titanium alloy

[Joseph N]

Hallo all,
I'm doing some tests with a heating structure from tungsten-titanium alloy, above which there is a silicon nitride layer for passivation. A room temperature fluid is applied on the SiN layer. It had worked ordinarily with resistance c.a. 1 kohm for around 5 hours, then the resistance suddenly jumped to 380 kohm, which seems nearly brocken. Acctually the current was constantly observed to be 5 mA before the drastic change. 
What could be the problem? Any advice would be appreciable.

win2