I measured the C-V curves of MOS capacitor in different frequencies by HP4284A precision LCR meter. When the frequency was low to be 10kHz, the C-V curve started to be oscillatory, but in some papers, the C-V curve can be measured in lower frequency such as 1kHz. I think the oscillation comes from the noise, but is it attributed to the MOS capacitor or the measurement system? What should I do if I want to measure the C-V curve in lower frequency?
You have probably capacitive coupling, therefore you run into the Problem that your MOSFET start to oscillate. You need to use shorter cables, smaller Amplitude of the oscillation Signal by HP4284A and think carefully about isolattion of the signals.
Hi Zhixiang Cheng
All the answers related to MOSCAP CV are available in one book.
It is the best book on MOSCAPs, please refer to MOS Physics and Technology by Nochollian and Brews.
http://as.wiley.com/WileyCDA/WileyTitle/productCd-047143079X.html
Please check first with what Dr. Sergey Bychikhin has mentioned to make sure the issue is not because of the connection or parasitic components.
Then you may also look into the DC sweep rate you use vs. the AC sweep rate. It would be best if you can post your measurement settings. Remember the measurement is done essentially by applying a certain amplitude of AC sine/cosine sweeping bias onto a DC sweeping bias. For this to work without oscillation, the DC sweep rate (V/s) need to be
Try to increase the ac signal amplitude or the capacitor area to check if it is not due to the low measured ac current at 10kHz.
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