Xiaolong Ma

Novel 14-nm Scallop-Shaped FinFETs (S-FinFETs) on Bulk-Si Substrate

In this study, novel p-type scallop-shaped fin field-effect transistors (S-FinFETs) are fabricated using an all-last high-k/metal gate (HKMG) process on bulk-silicon (Si) substrates for the first time. In combination with the structure advantage of conventional Si nanowires, the proposed S-FinFETs provide better electrostatic integrity in the channels than normal bulk-Si FinFETs or tri-gate devices with rectangular or trapezoidal fins. It is due to formation of quasi-surrounding gate electrodes on scalloping fins by a special Si etch process. The entire integration flow of the S-FinFETs is fully compatible with the mainstream all-last HKMG FinFET process, except for a modified fin etch process. The drain-induced barrier lowering and subthreshold swing of the fabricated p-type S-FinFETs with a 14-nm physical gate length are 62 mV/V and 75 mV/dec, respectively, which are much better than those of normal FinFETs with a similar process. With an improved short-channel-effect immunity in the channels due to structure modification, the novel structure provides one of possibilities to extend the FinFET scalability to sub-10-nm nodes with little additional process cost.

Device parameter optimization for sub-20 nm node HK/MG-last bulk FinFETs

Sub-20 nm node bulk FinFET PMOS devices with an all-last high-k/metal gate (HK/MG) process are fabricated and the influence of a series of device parameters on the device scaling is investigated. The high and thin Fin structure with a tapered sidewall shows better performance than the normal Fin structure. The punch through stop layer (PTSL) and source drain extension (SDE) doping profiles are carefully optimized. The device without SDE annealing shows a larger drive current than that with SDE annealing due to better Si crystal regrowth in the amorphous Fin structure after source/drain implantation. The band-edged MG has a better short channel effect immunity, but the lower effective work function (EWF) MG shows a larger driveability. A tradeoff choice for different EWF MGs should be carefully designed for the devices scaling.

Gate-All-Around Silicon Nanowire Transistors with channel-last process on bulk Si substrate

For the first time, a Gate-All-Around (GAA) Silicon Nanowire Transistor (SNWT) with one special nanowire channel-last (NCL) process technology on silicon (Si) substrate is reported. Different from the traditional approach that the nanowire channels are formed and released at the initial steps of the process flow, the NCL process features the release of nanowire channels in high-k/metal gate-last process during the integration of conventional bulk-Si FinFET. It provides a stable way for the introduction of nanowire transistors in the FinFETs process for mass productions. The fabricated n-type transistors with the effective nanowire diameter (DNW) of 12 nm∼17 nm and the gate length of 100 nm demonstrated excellent subthreshold characteristics (subthreshold swing = 64mV/V and drain induced barrier lowering = 24mV/V). Meanwhile, it’s found that the H2 baking process as well as the optimized interface gate oxidation on NW channels greatly improved the device’s SS and off-current parameters.