ehui Yu

Characteristics of carbon nitride films synthesized by single-source ion beam enhanced deposition system

Carbon nitride films on silicon (111) and (100) wafers and Ti/C substrates with nitrogen concentration up to 50 at. % have been prepared by ion beam enhanced deposition carried out in a single ion source system. The possibility of synthesis of carbon nitride films was investigated. The nitrogen concentration and the compositions of the films were analyzed by Rutherford backscattering which gave out the nitrogen concentration of the films ranging from 37 to 50 at. %, Fourier transform infrared spectroscopy, and x‐ray photoelectron spectra. The characteristics of C 1s peaks at 284.6, 285.9, 287.5, 289.5, eV and N  1s peaks at 396.0, 398.4, 399.9, 402.1 eV enabled us to analyze the compositions of the films. The results of the analyses indicate that various phases such as different carbon phases, a tetrahedrally bonded phase (β‐C3N4) and other carbon nitrides (the ratio of N/C varied from 0.5 to 1.1) are contained in the films. Furthermore the concentration of the tetrahedrally bonded phase increases with th...

Improvement of Al2O3 Films on Graphene Grown by Atomic Layer Deposition with Pre-H2O Treatment

We improve the surface of graphene by atomic layer deposition (ALD) without the assistance of a transition layer or surface functionalization. By controlling gas-solid physical adsorption between water molecules and graphene through the optimization of pre-H2O treatment and two-step temperature growth, we directly grew uniform and compact Al2O3 films onto graphene by ALD. Al2O3 films, deposited with 4-cycle pre-H2O treatment and 100-200 °C two-step growing process, presented a relative permittivity of 7.2 and a breakdown critical electrical field of 9 MV/cm. Moreover, the deposition of Al2O3 did not introduce any detective defects or disorders in graphene.

Dose-energy match for the formation of high-integrity buried oxide layers in low-dose separation-by-implantation-of-oxygen materials

High-quality low-dose separation-by-implantation-of-oxygen (SIMOX) silicon-on-insulator (SOI) wafers have been fabricated from a series of good matches of dose-energy combinations. The results reveal that a wafer fabricated at an optimum dose-energy match has a superior SOI layer with a low threading dislocation density, a high-integrity buried oxide (BOX) layer with a minimal detectable silicon island density and a low pinhole density. This work introduces an approach to flexibly control the thickness of both SOI and BOX layers, allowing the fabrication of ultrathin SIMOX wafers with ultrathin SOI and BOX layers, and improving the throughput capacity by selecting good dose-energy matches. A possible mechanism is discussed.

Property transformation of graphene with Al2O3 films deposited directly by atomic layer deposition

Al2O3 films are deposited directly onto graphene by H2O-based atomic layer deposition (ALD), and the films are pinhole-free and continuously cover the graphene surface. The growth process of Al2O3 films does not introduce any detective defects in graphene, suppresses the hysteresis effect and tunes the graphene doping to n-type. The self-cleaning of ALD growth process, together with the physically absorbed H2O and oxygen-deficient ALD environment consumes OH− bonds, suppresses the p-doping of graphene, shifts Dirac point to negative gate bias and enhances the electron mobility.

Direct growth of high-quality Al2O3 dielectric on graphene layers by low-temperature H2O-based ALD

A thin Al2O3 dielectric film was directly grown onto graphene layers without any surface treatment prior to H2O-based atomic layer deposition for the first time. The growth mechanism of Al2O3 dielectric film has been studied by changing the growth temperature and purge time. We found that the film morphology was influenced by the amount and distribution of physically adsorbed precursor molecules on the graphene, especially by physically adsorbed H2O molecules. Within an optimal temperature window, conformal and uniform Al2O3 thin films were obtained as confirmed by atomic force microscopy and transmission electron microscopy results. Raman spectroscopy revealed that no extra defects are generated in the graphene layers. Furthermore, the low leakage current and interface traps in dual-gated graphene field-effect transistors demonstrate the high-quality dielectric/graphene stack.

Improvement of SOI Trench LDMOS Performance With Double Vertical Metal Field Plate

In this paper, a novel high-voltage trench lateral double-diffused metal-oxide-semiconductor field effect transistor (TLDMOS) based on silicon-on-insulator technology is proposed. The new structure is characterized by a double vertical metal field plate (DVFP) in the oxide trench, which is surrounded by heavily doped N/P pillars [superjuction (SJ)]. The DVFP introduces five new electric field peaks in the bulk of drift region compared with the conventional TLDMOS, leading to the breakdown voltage (BV) increase. Furthermore, the DVFP and SJ provide an electrons accumulation layer at the interface of the N pillar and oxide trench under the ON-state, reducing the specific ON-resistance (RON). With the 2-D device simulation, a BV of 840 V and a RON of 60.2 mQ · cm2 are realized on a 25-μm-thick SOI layer and 0.5 μm buried oxide layer, and the Baligas figure of merit [(FOM), FOM = BV2/RON] of 11.4 MW/cm2 is achieved, breaking through the silicon limit.

Effects of rapid thermal annealing on the properties of AlN films deposited by PEALD on AlGaN/GaN heterostructures

Aluminum nitride (AlN) films have been deposited on AlGaN/GaN heterostructure substrates by plasma enhanced atomic layer deposition (PEALD). Different annealing treatments were adopted to change film structure and improve performance. Chemical composition, crystallinity, and electrical properties were studied for AlN films. The results show that some crystal grains appear in the films after annealing at a temperature of over 800 °C. The film crystalline quality increases as the annealing temperature rises. The N–O–Al bond decomposes during the high temperature annealing in N2, and some new N–Al bonds are formed in the AlN films. Annealing promotes the elemental interdiffusion between the films and the substrates. High-temperature annealing at 1000 °C in a nitrogen atmosphere can effectively promote complete nitridation of the AlN film, reduce the nitrogen vacancies, and cause the AlN film to form a semiconductor-like structure.

TCAD study on gate-all-around cylindrical (GAAC) transistor for CMOS scaling to the end of the roadmap

In this paper, we report TCAD study on gate-all-around cylindrical (GAAC) transistor for sub-10-nm scaling. The GAAC transistor device physics, TCAD simulation, and proposed fabrication procedure have been discussed. Among all other novel fin field effect transistor (FinFET) devices, the gate-all-around cylindrical device can be particularly used for reducing the problems of conventional multi-gate FinFET, improving device performance, and scaling-down capabilities. With gate-all-around cylindrical architecture, the transistor is controlled essentially by infinite number of gates surrounding the entire cylinder-shaped channel. Electrical integrity within the channel is improved by reducing the leakage current due to the non-symmetrical field accumulation such as the corner effect. Our proposed fabrication procedure for making devices having the gate-all-around cylindrical (GAAC) device architecture is also discussed.

Interfacial structures and electrical properties of HfAl2O5 gate dielectric film annealed with a Ti capping layer

HfAl2O5 gate dielectric film with an O-gettering Ti capping layer treated with rapid thermal annealing process and its interfacial structure and electrical properties were reported. X-ray reflectivity measurements and x-ray photoelectron spectroscopy suggested that the interfacial layers were composed of a 0.5nm HfAlSiO layer and a 1.5nm Six(SiO2)1−x (x<1) layer for the as-deposited film. However, for the annealed film, HfAlSiO layer was not found and the 1.5nm Six(SiO2)1−x transformed to a 1nm SiO2. The electrical measurements indicated that the equivalent oxide thickness decreased to 2.9nm, and the leakage current was only 70μA∕cm2 at the gate bias of 10MV∕cm for the annealed film.

Al2O3/NbAlO/Al2O3 sandwich gate dielectric film on InP

Al2O3/NbAlO/Al2O3 sandwich dielectric films were grown on InP substrate and annealed. X-ray reflectivity measurements suggested that 1.0 nm interfacial layer existed at InP interface, x-ray diffraction and high resolution transmission electron microscopy indicated the films were crystallized. X-ray photoelectron spectra indicated the oxidization of InP substrate, and the valence-band offset between the dielectric film and InP interface was calculated to be 3.1 eV. The electrical measurements indicated that the leakage current density was 40 mA/cm2 at gate bias of 1 V, and the equivalent oxide thickness and the dielectric constant were 1.7 and 20 nm, respectively.