#homecmos IRC log for Tuesday, 2011-11-08

--- Tue Nov 8 201100:00
berndjazonenberg, i don't get why *high*-k dielectrics are good for gate insulation.  doesn't that increase the gate capacitance?17:03
azonenbergberndj: but it also decreases leakage17:45
azonenbergi think17:45
azonenbergand lets you make the dielectric thinner17:45
azonenbergby contrast you want low-K for ILD17:46
azonenbergso you dont have capacitive coupling between wires etc17:46
azonenbergor wire capacitance getting in the way as much17:46
azonenbergberndj: i think it also lets you make the gate smaller17:49
berndjILD?17:50
azonenberginter-layer dielectric17:50
berndjokay so it's more like it *happens* to have high-K, but that isn't the reason you use it for gate insulation: instead you're using it for the higher dielectric strength it also has?17:51
azonenbergThey're the same thing17:51
azonenberghigher dielectric strength will increase capacitance17:51
berndjerr, correlated, i'm sure, but not the same thing?17:51
azonenbergAnd doing a little bit of reading it seems that really thin gate dielectrics have troubles with leakage17:52
berndjSF6 for example wouldn't follow that correlation too well17:52
azonenbergSo the way to compensate is to use a *thicker* dielectric17:52
azonenbergbut use high-K to get the same capacitance17:52
berndjbut you *don't* want capacitance in a gate, surely?17:53
azonenbergI think you do17:53
azonenbergthe higher the capacitance per unit area, the more charge you can put across it and thus the lower your on resistance17:54
berndjthis is getting confusing :(17:54
azonenbergYeah17:54
azonenbergTransistors are something i have not studied much17:54
azonenbergmy focus has been MEMS so far17:55
berndjwhat you said there re charge makes sense, but i thought it's the E field that inverts the polarity of the channel17:55
azonenbergno idea, again18:00
azonenbergthis is something i've been meaning to study for a while18:00
--- Wed Nov 9 201100:00

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