You could have stringers, which are thin "strings" of metal that run along
steps in the underlying insulator due to incomplete etching.
You can check this by probing two adjacent metal lines, hooking the probes
up to a variable power supply and monitoring the current.
Turning the voltage up from zero, you would see the current rise, then
suddenly drop when the stringer melts. This often leaves a visible dark
mark.

    --Kirt Williams

----- Original Message -----
From: "Ho Yin Chan" 
To: 
Sent: Tuesday, March 25, 2008 2:28 PM
Subject: [mems-talk] PECVD oxide conductivity


> Hi all,
>
>  I am putting Ti/Au metal lines on top of 1um PECVD oxide at ~380C. I
> found
> there is finite reisstance between the metal lines. Those are parallel
> lines
> with 100um wide and 2mm long. They are seperated at a distance of 40um. I
> am
> curious the reason behind it. I tried to measure the resistivity of PECVD
> oxide. It shows > 10E14 Ohm cm.