Abstract
The lateral band-to-band tunneling (L-BTBT) leakage mechanism increases the OFF state current and prevents the junctionless transistor from scaling. The effect of L-BTBT on FIN shaped gate Junctionless field effect transistor(JLFET) with the ground plane (GP) in oxide has been investigated. The proposed device is simulated using 3-D Silvaco TCAD and shows that it can mitigate the L-BTBT and leads to efficient volume depletion which relaxes the requirements of ultra-thin silicon thickness and high workfunction of the gate electrode. The results show significantly reduced OFF-state current and high Ion/Ioff ratio even at scaled gate length beyond 10 nm along with the reduction in drain induced barrier lowering and threshold voltage roll-off. Thus, the proposed device shows better performance at sub-10 nm node.
Highlights
Trends in the semiconductor industry are towards scaling down the transistor size to reduced delay, power, and increased packing density
This can be attributed to the parasitic BJT that is being triggered due to hole accumulation resulting from lateral band to band tunneling at the channel drain interface
The ground plane (GP) spans the length of the device, and it can be considered as the effect of increasing the base width of the parasitic BJT and the current due to the parasitic transistor is reduced as it is inversely proportional to the width of the base width of transistor
Summary
Trends in the semiconductor industry are towards scaling down the transistor size to reduced delay, power, and increased packing density. The device is turned off by gate semiconductor work function difference and requires a thin channel and high metal work function above 5.5eV [10] to successfully turn off the device Another source of increased off state current arises from lateral band to band tunneling at the interface of the channel and drain. Because of the significant proximity of the drain and the channel region, the valence band of the channel region overlaps with the conduction band of the drain region and if the tunneling width is small enough, it leads to the lateral band-to-band tunneling (BTBT) leaving behind holes in the channel region for an n-type junctionless transistor These accumulated holes form a parasitic bipolar transistor(BJT) with the adjoining source and drain region and are the dominant mechanism for increased leakage current in the off state. Channel doping(n-type) (/cm3) Gate oxide material Gate oxide thickness (nm) Gate workfunction (eV) Silicon Film Height (nm) Silicon Film Width (nm) Gate length (nm) Ground plane depth (nm) Ground plane thickness (nm) Ground plane doping (p-type) (/cm3)
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