This sounds like defects or contamination on the sides following dicing. If
you have Si particles or other contamination shorting the oxide it will
conduct, burn itself, another defect will conduct (or breakdown) etc.

shay

-----Original Message-----
From: Kimi
Subject: [mems-talk] electrical insulation of SOI wafer

we dice samples (about 1cm sq) without pattern from SOI wafer (purchased)
and fusion bonded wafer with 1um burried oxide. Apply DC voltage (10~180V)
across device layer and handle layer silicon (both p-type, 1~10 Ohm-cm).
Measure the current at different voltage level and found some samples have
resistance over tens of MOhm even over 100V but some will deteriorate
rapidly to only KOhm at high voltage. For MOhm samples, the current is
stable.  For those samples with low resistance, the current increase
gradually to certain level then suddenly drop but pick up gradually again in
a cyclic fashion.  the poor oxide insulation quality and cyclic behavior
will cause future device stability problem even if handle layer is grounded.
what may be the cause, trapped mobile ion, oxide contamination? any proper
way to check oxide insulation quality of burried oxide in SOI wafer or oxide
film on si?