Dashen Shen

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.

Dielectric properties of AlN thin films formed by ion beam enhanced deposition

Abstract AlN thin films were prepared through IBED. The microstructure and electronic characteristics of AlN films were studied through XPS and C – V / I – V test. N 2 gas added into IBED system during deposition could enhance N/Al ratio near to stoichiometrical structure and improve dielectric properties of AlN films. Some important dielectric parameters for AlN thin films were obtained.

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.

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.

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.

Competitive Si and La effect in HfO2 phase stabilization in multi-layer (La2O3)0.08(HfO2) films

The effect of Si diffusion in HfO2 and the presence of La on phase transformation were investigated. Tetragonal HfO2 structures exhibited high permittivity, and the addition of exotic atoms to HfO2 facilitated tetragonal phase transformation. In multi-layer (La2O3)0.08(HfO2) films, the top HfO2 layer was transformed into a perfect tetragonal structure, and the bottom HfO2 layer near the interfacial layer was of a cubic structure, after annealing at 800u2009°C. The permittivity reached 50–60. Si diffusion into the HfO2 film stabilized the tetragonal structure, and La incorporation into HfO2 facilitated the transition of the cubic structure.

Interfacial and Electrical Characterization of HfO2 Gate Dielectric Film with a Blocking Layer of Al2O3

HfO<inf>2</inf> gate dielectric films with a blocking layer of Al<inf>2</inf>O<inf>3</inf> inserted between HfO<inf>2</inf>/Si were treated with rapid thermal annealing process at 700°C. The interfacial structure and electrical properties are reported. X-ray photoelectron spectroscopy indicated that the interfacial layer of SiO<inf>x</inf> transformed into SiO<inf>2</inf> after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. High-resolution transmission electron microscopy showed that the interfacial layer was composed of SiO<inf>2</inf> for the annealed film with a blocking layer. The electrical measurements indicated that the equivalent oxide thickness decreased to 2.5nm and the fixed charge density decreased to −4.5×10¹¹/cm² in comparison with the same thickness of HfO<inf>2</inf> films without the blocking layer. Al<inf>2</inf>O<inf>3</inf> layer could effectively prevent the diffusion of Si into HfO<inf>2</inf> film and improve the interfacial and electrical performance of HfO<inf>2</inf> film.

Direct growth of Sb2Te3 on graphene by atomic layer deposition

The direct growth of Sb2Te3 on graphene is achieved by atomic layer deposition (ALD) with pre-(Me3Si)2Te treatment. The results of atomic force microscopy (AFM) indicate Volmer–Weber island growth is the dominant growth mode for ALD Sb2Te3 growth on graphene. High resolution transmission electron microscopy (HRTEM) analysis reveals perfect crystal structures of Sb2Te3 on graphene and no interface layer generation. The characterization of X-ray photoelectron spectroscopy (XPS) implies the impermeability of graphene can maintain Sb2Te3 intact and isolate the adverse effects of substrates. Our study provides a step forward to grow high quality Sb2Te3 at low temperature and expand the potential applications of graphene in ALD techniques.

Low-temperature plasma-enhanced atomic layer deposition of HfO2/Al2O3 nanolaminate structure on Si

HfO2/Al2O3 nanolaminate was deposited on a Si substrate by plasma-enhanced atomic layer deposition at 150u2009°C with in situ plasma treatment. Unilayer HfO2 and Al2O3 films were prepared for comparison. Films were treated by rapid thermal annealing at 870u2009°C in a nitrogen atmosphere for 30u2009s. Al atoms in the HfO2/Al2O3 nanolaminate diffuse into HfO2 layers during rapid thermal annealing, facilitating the formation of tetragonal HfO2. The HfO2/Al2O3 nanolaminate has an effective dielectric constant of 20.7, a breakdown electric field of 7.4 MV/cm, and leakage current of 2.3u2009×u200910−5u2009mA/cm2 at a gate bias of Vgu2009=u2009−1u2009V. The valence band offset, conduction band offset, and the band gap of the film are 2.75, 1.96, and 5.83u2009eV, respectively.