Papers by Keyword: Atomic Layer Deposition ALD

Abstract: We investigate the perpendicular magnetic anisotropy dependence on the AlO capping layer in Pt/Co/AlO films. AlO was deposited on Pt/Co films by RF magnetron sputtering and atomic layer deposition (ALD) with varying thickness. It is found that the prolonged deposition of thick AlO layers by RF magnetron sputtering causes significant damage to the Pt/Co underneath while AlO layers formed by ALD can be of arbitrary thickness with no damage to the magnetic properties of the films. The decline of the magnetic properties can be attributed to the method of AlO deposition for each process. In the RF magnetron sputtering, AlO atoms with high kinetic energy are ejected from a sputter target resulting in the degradation of Pt/Co films, while the process of deposition of AlO by ALD is governed by a series of chemically reactive condensations allowing for arbitrary deposition thickness of AlO.

Abstract: Scaling of CMOS structures through the deep sub-micron range and into the nano-scale range (< 100 nm) has posed a number of difficult problems for processing technology. One main technological approach has been to improve the uniformity and conformality of deposited layers. As the Atomic Layer Deposition (ALD) has already demonstrated that it can overcome many of the limitations of current film deposition techniques, it seems to be the solution for very conformal layers of high quality on severe topography. The ALD method has been developed already in the 1970’s by Tumo Suntola and co-workers [1-4]. However, it has been in the past a rather unused method in the semiconductor industry. This has recently changed. During the last couple of years, the large semiconductor companies have spent a lot of effort in the utilization of ALD, but until now a production worthy ALD tool with low ‘Cost-of-Ownership’ (CoO) numbers was not available. One reason for the late introduction of ALD is that the method is rather slow compared with the state of art methods like CVD, PECVD and PVD. Nevertheless, due to the outstanding properties of the ALD technique, the drawback of slow deposition rate may be balanced by the parallel processing of many wafers in semiconductor furnaces, as described here.

Abstract: We have investigated the electrical properties of metal-oxide-semiconductor (MOS) capacitors with atomic-layer-deposited La2O3, thermal-nitrided SiO2, and atomic-layer-deposited La2O3/thermal-nitrided SiO2 on n-type 4H-SiC. A significant reduction in leakage current density has been observed in La2O3 structure when a 6-nm thick thermal nitrided SiO2 has been sandwiched between the La2O3 and SiC. However, this reduction is still considered high if compared to sample having thermal-nitrided SiO2 alone. The reasons for this have been explained in this paper.

Abstract: The organic-inorganic field effect transistors (OIFETs) with ZnS active layer were fabricated on the ITO/glass substrate using cross-linked PVP (poly-4-vinylphenol) as a gate insulator. ZnS semiconductor films were prepared by the atomic layer deposition method. In the case of cross-linked PVP film, the leakage current and capacitance were about 1× 10-8 A and 12 nF/cm2, showing good gate insulation property. The carrier concentration and mobility of ZnS film deposited on SiO2/Si wafer was found to be -9.4×1015 cm-3 and 49.0 cm2/ V·sec, respectively. For the OIFET devices with ITO/PVP/ZnS/Ti:Au structure, the carrier mobility was about 1.9 cm2/V·sec. From the AFM images, lower mobility in the OIFET device compared with ZnS film on SiO2/Si substrate may be attributed to a rough surface morphology of ZnS film.

Abstract: ZnS thin films were grown by Atomic Layer Deposition (ALD) method with Diethyl- Zinc (DEZ) and hydrogen sulfide (H2S) for the application of a channel layer of OITFT (Organic-Inorganic Thin-Film Transistor). ZnS has many advantages such as high channel mobility, high deposition rate, transparency at room temperature due to the broad band gap (bandgap of ZnS : 3.7 eV), nontoxic characteristic, low resistivity, and less sensitive about oxidation than ZnO. The deposition rate of the ZnS films in our system was about 1.6 Å/cycle. ZnS film was characterized by AES, XRD, Hall-effect measurement.

Abstract: Nanocrystalline diamond compact possesses not only the advantageous performance of polycrystalline diamond but also the high strength and the high toughness of nano-ceramics. However, single-phase nanocrystalline diamond compact is very difficult to sinter because of a huge amount of oxygen-containing and nitrogen-containing functional groups absorbed on the surface of nanocrystalline diamond. In this paper, atomic layer deposition (ALD) method has been used to coat nanocrystalline diamond with titanium, which will promote the bonding of nanocrystalline diamond as the bond in polycrystalline diamond. In vacuum, the H2 and TiCl4 reactants were employed alternately in an ABAB… binary reaction sequence to achieve Ti layer, which reacted with diamond matrix and formed TiC in the coating, realizing strong chemical bonding between the coating and the diamond. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to study the structure and the morphology of the coating. The results confirmed the formation of titanium carbide at the depositing temperature 500°C. The darker spots and strips observed on nanocrystalline diamond particles by TEM were proved to be TiC and the nucleation and subsequent growth of TiC preferentially occurred in the defects as twin zones and dislocation areas on diamond surfaces.

Abstract: Aluminium oxide and titanium oxide films were deposited using the Atomic Layer Deposition method on n-type 4H SiC and p-type Si {001} substrates, with doping 6×1015cm-3 and 2×1016cm-3, respectively, and on 1.2 kV PiN 4H SiC diodes for passivation studies. The Al2O3 and SiC interface was characterised for the existence of an effective negative charge with a density of 1×1012-2×1012 cm-2. The dielectric constant of Al2O3 as determined from capacitance-voltage data was about 8.3. The maximum electric field supported by the Al2O3 film was up to 7.5 MV/cm and 8.4 MV/cm on SiC and Si, respectively.