Yes I think you are right. With temperature the threshold voltage varies thus impacting the overdrive voltage.

Vt (threshold voltage of a n-MOSFET) decreases with increasing temperature meaning gate overdrive (Vgs-Vt) will increase with substrate temperature > 300 K at a particular gate voltage. But channel mobility will be severely affected by increase of substrate temperature > 300 K (phonon scattering) and usually reduction of channel mobility wins over gate overdrive voltage increase to ideally reduce drive current Ion substantially than room temperature (300K). Except for high temperature electronics where robust and wide-band gap semiconductors are used, silicon based digital scaled ULSI electronics rarely operates the device higher than 300 K.

Arjun Shetty: If you are working with NVM memories, channel hot carrier injection and FN-tunneling are used for programming and erase purpose. In that case high temperature operation of the substrate can lead to charge loss or retention loss due to leakage current increase at higher temperature. At higher temperature Ion/Ioff ratio degrades severely as Ion is decreased and Ioff is increased and programming and retention can be of huge problem. From digital electronics perspective, let's say you are using highly scaled device. So the channel doping will be at degenerate high level which will trigger many-body effects at higher temperature more strongly. Since mean free path between carrier-carrier scattering and carrier-lattice scattering is decreased as temperature is increased, carrier carrier scattering will add up to phonon scattering to reduce transport channel mobility severely. Have you found any success though at SanDisk by operating NVM memories programming, erasing and retention all done at higher substrate temperatures > 300 K ?

Arjun: Some other facts wanted to share since I believe your question is with regard to NVM memory programming and erasure speed enhancement by operating at higher substrate temperature, that is what I am guessing. Although programming and erasure both are done by currents from gate to channel, if channel hot carrier method is used, carrier carrier scattering at higher temperature will randomize the mometumn and the carrier velocity will not be as high as 300 K value to surmount the oxide barrier. As band gap narrows with higher temperature, conduction band oxide barrier is reduced and this will enhance F-N tunneling based programming and erasure. So at higher temperature F-N tunneling might give faster programming and erasure speed than channel hot carrier programming which is strictly inefficient at higher temperature. Problem is when charge retention needs to be longer and since conduction band barrier offset to oxide is reduced for narrowed band gap, charge loss and leakage for sustained memory set operation cannot be avoided. I do not know whether you contemplated your thought at this aspect of analysis.

Sincerely

Dr Nabil Shovon Ashraf.r

Dear Prof Nabil Shovon Ashraf: Thank you for the detailed explanation. My main concern was to understand how over drive voltage and drive current is affected by temperature and your first comment managed to answer that. I understand that drive current reduces with increase in temperature primarily because of the decrease in mobility.

Regarding your other comment in your second post, yes we do have success with programming and data retention at temperatures as high as 85C. Of course with increase in temperature there is increase in charge loss due to data retention and it takes shorter time for the errors to become uncorrectable.

Regarding your last comment, as mentioned earlier, my question was regarding effect of temperature on drive current and not on program or erase performance. But yes, what you mentioned is correct, we do see an improvement in program performance with increase in temperature.

Arjun: I was glad to know all my answers were appreciated by you and found informative for your queries. Would you please then recommend all my answers to your query to justify myself as an expert analyst in giving answers to other researchers who put questions in ResearchGate. I have given answers to questions in solid state device physics and device modeling to a very high number of queries and it worked for most of these people. I will be waiting for your recommendation.

Sincerely,

Dr. Nabil Shovon Ashraf.