41stvs. 2ndOrder nMOS I-V65 nm IBM process, VDD= 1.0 V
52ndOrder Current Model Ion= Ids@ Vgs= Vds= VDD SaturationIoff= Ids@ Vgs= 0, Vds= VDD Cutoff
7DIBLElectric field from drain affects channelMore pronounced in small transistors where the drain is closer to the channelDrain-Induced Barrier Lowering–Drain voltage also affects VtHigh drain voltage causes current to increase.~ 0.1ttdsVVVttdsVVV
9LeakageWhat about current in cutoff?Simulated resultsWhat differs?–Current doesn’tgo to 0 in cutoffImplications:1) output < VDD2) static power3) memory forgets
10Gate-Induced Drain LeakageOccurs at overlap between gate and drain–largest when drain = VDD, gate < 0–Thwarts efforts to reduce subthreshold leakage with gate voltage < 0, but also impacts gate = 0
11Subthreshold LeakageSubthreshold leakage exponential with Vgsn is process dependent–typically 1.3-1.7Rewrite relative to Ioffon log scaleS ≈ 100 mV/decade @ room temperature00e1egstdssbdsTTVVVk VVnvvdsdsII
FINFET DIBLFirst finFETs were manufactured on an insulating layer. Current can't flow "underneath" the gate when the transistor is OFF ==> reduced leakage. Later techniques for reducing leakage current from flowing in the bulk ==> allowed Bulk finFETs. High doping gradients along the height of the fin prevent current from flowing in the bulk.