Narrow Results

In this work we simulate the dependence of the amplitude of the random telegraph noise (RTN) on the gate overdrive (overload) for SOI FinFET with a cross section of rectangular and trapezoidal channels. It is shown that in the sub-threshold area when a single interface charge is detected in the middle of the RTL interface, the amplitude of the RTN is much higher for the cross section of the trapezoidal channel. In contrast, the amplitude of RTN is higher for a rectangle than for a cross section of a trapezoidal channel when the charge of an interface is detected at the upper channel interface. We also consider the dependence of the RTN amplitude on the position along the transistor channel, the charge of a single interface, which is detected at the upper interface, and on the side channel interface.

The economic health of the semiconductor industry requires substantial scaling of chip power, performance, and area with every new technology node that is ramped into manufacturing in two year intervals. With no direct physical link to any particular design dimensions, industry wide the technology node names are chosen to reflect the roughly 70% scaling of linear dimensions necessary to enable the doubling of transistor density predicted by Moore’s law and typically progress as 22nm, 14nm, 10nm, 7nm, 5nm, 3nm etc. At the time of this writing, the most advanced technology node in volume manufacturing is the 14nm node with the 7nm node in advanced development and 5nm in early exploration. The technology challenges to reach thus far have not been trivial. This review addresses the past innovation in response to the device challenges and discusses in-depth the integration challenges associated with the sub-22nm non-planar finFET technologies that are either in advanced technology development or in manufacturing. It discusses the integration challenges in patterning for both the front-end-of-line and back-end-of-line elements in the CMOS transistor. In addition, this article also gives a brief review of integrating an alternate channel material into the finFET technology, as well as next generation device architectures such as nanowire and vertical FETs. Lastly, it also discusses challenges dictated by the need to interconnect the ever-increasing density of transistors.

In this work, optimization of selective epitaxy growth (SEG) of SiGe layers on source/drain (S/D) areas in 14nm node FinFETs with high-k & metal gate has been presented. The Ge content in epilayers was in range of 30%-40% with boron concentration of 1-3 × 10²⁰ cm⁻³. The strain distribution in the transistor structure due to SiGe as stressor material in S/D was simulated and these results were used as feedback to design the layer profile. The epitaxy parameters were optimized to improve the layer quality and strain amount of SiGe layers. The in-situ cleaning of Si fins was crucial to grow high quality layers and a series of experiments were performed in range of 760−825 °C. The results demonstrated that the thermal budget has to be within 780−800 °C in order to remove the native oxide but also to avoid any harm to the shape of Si fins. The Ge content in SiGe layers was directly determined from the misfit parameters obtained from reciprocal space mappings using synchrotron radiation. Atomic layer deposition (ALD) technique was used to deposit HfO₂ as high-k dielectric and B-doped W layer as metal gate to fill the gate trench. This type of ALD metal gate has decent growth rate, low resistivity and excellent capability to fill the gate trench with high aspect-ratio. Finally, the electrical characteristics of fabricated FinFETs were demonstrated and discussed.

We have investigated the short-channel effect (SCE), floating-body effect, and three-dimensional coupling effect in triple-gate MOSFET with various fin widths, gate lengths and number of fins. It is found that the SCE of these devices is alleviated as the fin width shrinks and does not depend on the number of fins. The gate-induced floating-body effect (GIFBE) is visible even in fully depleted (FD) triple-gate transistors when the film-buried oxide (BOX) interface is swept from depletion to accumulation by the back-gate bias. The 3-D coupling effect in vertical, lateral, and longitudinal directions was investigated for different channel geometries. The biasing condition which enables the simultaneous activation of all channels and gives rise to volume inversion is discussed.

The Screen-Grid Field Effect Transistor (SGrFET) is a planar MOSFET-type device with a gating configuration consisting of metal cylindrical fingers inside the channel perpendicular to the current flow. The SGrFET operates in a MESFET mode using oxide insulated gates. The multi-gate configuration offers advantages for both analog and digital applications, whilst the gate cylinder holes can be exploited for bio-applications. In this manuscript TCAD results are presented on the analog and digital performance of the Screen-Grid Field Effect Transistor. The results are compared to the operation of an SOI-MOSFET and a finFET.

We have fabricated and investigated several types of GaN MOSFETs with normally-off operation. The recessed-gate GaN MOSFET is preferred for normally-off operation, because the threshold voltage (V_th) of the device can be easily controlled, but it suffers from relatively modest current drivability which must be improved by adopting appropriate device structure and/or process. Enhanced performances have been achieved in this work by combining the recessed-gate technology with additional processes, such as: the post-recess tetramethylammonium hydroxide (TMAH) treatment to remove the plasma damage, the post-deposition annealing of gate oxide to decrease the gate leakage current, the re-growth of n+ GaN layer for source/drain to improve the access resistance and V_th uniformity, the stress control technology to achieve extremely high 2-D electron-gas density (2DEG) on source/drain and decrease the series resistance, and the use of the p-GaN back-barrier to decrease the buffer leakage current. The GaN-based FinFET with very narrow fin was also investigated as a possible candidate for high performance normally-off GaN MOSFETs.