Search

Impact of source/drain contacts on the operation performance of three-dimensional (3-D) zinc-oxide (ZnO) logic inverters is explored in this work. The 3-D inverters consisting of a load vertically stacking on a driver were constructed with the film-profile-engineered (FPE) approach. Use of an ultra-thin ZnON contact layer is proposed and demonstrated to be effective in reducing the source/drain (S/D) series resistances (R SD ) of the devices. From the material characterization, the improvement in the electrical characteristics is attributed to the suppression of an insulating interfacial oxide layer present at the contact interface which may impede the carrier transport. Measurement results of inverters indicate that the voltage gain can be improved from 9.7 V/V to 13.2 V/V as the scheme is implemented.

IGZO 3-D film-profile-engineered (FPE) inverters were fabricated and characterized. The unipolar load and driver thin-film transistors (TFTs) were stacked vertically not only for the sake of saving footprint, but also for the flexibility of threshold voltage adjustment by the lengths of suspended hardmask. The proposed 3-D inverters demonstrate full-swing switching with a voltage gain as high as 13.6 V/V at an operating voltage of 5 V. The long-term stability was investigated in terms of the voltage gain, transconductance (gm) and threshold voltage (Vth) shift. Following 4 months, degradation in the voltage gain of the inverter in company of reduced gm and positive V th shift for the drive TFT is attributed to the outgassing of hydrogen.

In this letter, we demonstrate 0.6- $\mu \text{m}$ ZnON thin-film transistors (TFTs) with the field-effect mobility of 71 cm $^{\mathrm {\mathbf {2}}}$ /V-sec, which to the best of our knowledge is the highest value ever reported on submicrometer oxide–semiconductor TFTs. The drive current, field-effect mobility, and subthreshold slope of ZnON TFTs are significantly improved as compared with their counterpart ZnO TFTs of the same channel dimensions and structure. Such an improvement in the field-effect mobility primarily results from a considerable reduction in the series source/drain (S/D) resistances because of suppression in an interfacial layer formation between Al S/D pads and the channel layer.

Short-channel zinc oxynitride (ZnON) thin-film transistors (TFTs) were fabricated based on the film profile engineering in combination with e-beam lithographical patterning. ZnON films were deposited using reactive magnetron sputtering in N 2 /O 2 ambient and exhibit a Hall mobility of 95 cm2/V-s. A ZnON TFT with channel length of 147nm shows high on/off current ratio of 5×107 and field-effect mobility of 9.1 cm2/Vs, which are superior or comparable to their counterparts of IGZO or ZnO TFTs.

This work reports the first experimental submicron and sub-100 nm ZnON TFTs with excellent performance. Field-effect mobility values as high as 55 and 9.2 cm2/V-s were measured from ZnON TFTs with channel lengths of 0.5 μm and 75 nm, respectively. Those are the highest values ever reported on oxide-semiconductor TFTs of comparable channel length. The results confirm ZnON TFTs as an effective building block for the construction of BEOL circuits integrated in a chip.