Hi Vejay
I have written the following to Chieh-Hsiao concerning fF measurements

'Hi Chieh-Hsiao Wang
I have once measured capacitances between interconnecting lines. These
lines were connecting a Si-membrane microphone and an IC chip. I had made
simulations on this structure and found capacitances of around 5-50 fF. So
I had to use a very sensitive instrument: HP- impedance analyser. I also
had to use shielded cables, four-point measurements (this is done with four
probes) , an electrical shielded probe station. Parasitics had to be
cancelled out with a compensation procedure built-in the analyser. These
were of the order 20-30fF, which is very high. Humidity of air had to be
controlled in order to avoid instability of the measurement. The
theoretical calculations turned out to be correct so measurement was
prooved to be possible.
If you have further questions I would be pleased to answer you.
Mounir Ennabli, Development Engineer.'
If you have any questions please do not hesitate to ask me
Regards