H. L. Seng

The impact of layer thickness of IMP-deposited tantalum nitride films on integrity of Cu/TaN/SiO2/Si multilayer structure

Abstract This work concentrates on the diffusion barrier stability of very thin tantalum nitride films with different thickness (10, 20 and 30 nm) sputter-deposited on silicon dioxide in the Cu/TaN/SiO2/Si multiplayer structure. The impact of varying layer thickness and influence of post deposition annealing on the crystal structure, resistivity, intermixing and reactions at the interfaces were studied by using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry. The results revealed that the thinner the film thickness of tantalum nitride, the more severe the reactions at the interface of copper–tantalum nitride and consumed more conductive Cu. Accelerated grain growth and/or agglomerations were also observed in all Cu surfaces. All the structures show a similar degradation process and were found to be stable up to 450°C for 35 min.

Ge nanocrystals in lanthanide-based Lu2O3 high-k dielectric for nonvolatile memory applications

Ge nanocrystals embedded in lanthanide-based high-k dielectric (amorphous Lu2O3 in this work) were formed using pulsed laser deposition followed by rapid thermal annealing in N2 ambient. The formation and evolution of the Ge nanocrystals have been studied using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) in conjunction with depth profiling, and secondary ion mass spectroscopy (SIMS) analysis. Plan-view TEM images indicated that the formation of nanocrystals was first initiated during the deposition process. The annealing treatment significantly enhanced the nucleation of Ge nanocrystals, resulting in a high areal density of 7×1011cm−2 Ge nanocrystals with a mean size of about 6nm in diameter in the amorphous Lu2O3 matrix. XPS depth profile analysis revealed that Ge nanocrystals were predominantly formed from the precipitation of Ge nuclei from the oxide phase. A low annealing temperature of 400°C was sufficient to dissociate the GeO2 and GeOx leading to the formation of ...

Liquid-phase epitaxial growth of amorphous silicon during laser annealing of ultrashallow p+/n junctions

We have investigated the effect of laser annealing on the recrystallization of the preamorphized layer during the formation of ultrashallow p+/n junctions. The results from channeling Rutherford backscattering spectrometry clearly indicate that the preamorphized layer has been completely annealed with a single-pulse laser irradiation at 0.5 J/cm2. These data are further verified by high-resolution cross-sectional transmission electron microscopy. It is proposed that the preamorphized layer has recrystallized to a single-crystalline structure via liquid-phase epitaxy. No observable extended defects are present in the recrystallized region after laser annealing.

Direct measurement of proton-beam-written polymer optical waveguide sidewall morphorlogy using an atomic force microscope

Proton-beam writing (PBW) is a direct-write micromachining technique capable of fabricating low-loss single-mode polymer waveguides with straight and smooth sidewalls. Recently, the sidewall morphologies of such proton beam written polymer waveguide structures were directly measured using an atomic force microscope (AFM). Statistical information such as the rms roughness and the correlation length of the sidewall profile obtained from the AFM scans allows us to quantify the quality of the sidewalls and optimize the fabrication parameters using PBW. For structures fabricated using a stage scanning speed of ∼10μm∕s, a rms roughness of 3.8±0.3nm with a correlation length of 46±6nm was measured.

Synthesis of germanium nanocrystals in hafnium aluminum oxide matrix

An examination on the effect of annealing temperature and duration, and the germanium (Ge) concentration on the growth of Ge nanocrystals in hafnium aluminum oxide (HfAlO) matrix, was carried out using a combination of Raman spectroscopy, transmission electron microscopy, and secondary ions mass spectrometry techniques. We found Ge nanocrystals in the HfAlO matrix with a Ge content of 10.5 at. % when annealed at 800 °C. At a relatively higher content of Ge at 23.3 at. % in HfAlO film, a significant outdiffusion of Ge at the film surface or diffusion into the Si substrate occurred, and this imposes a narrow annealing condition for the formation of nanocrystals. We attribute the different nanocrystal formation characteristics in the HfAlO and silicon oxide matrices to the difference crystallization temperatures of HfAlO and silicon oxide films.

Probing the SiGe virtual substrate by high-resolution channeling contrast microscopy

Relaxed, epitaxial SiGe layers with low densities of threading dislocations are grown by linearly grading the Ge composition. However, such compositionally graded SiGe layers (virtual substrates) often result in a cross hatch surface morphology which affects subsequent device processing. Here, we report on high-resolution channeling-contrast-microscopy (CCM) measurements on such virtual substrates grown by gas-source molecular-beam epitaxy and low-pressure chemical vapor deposition. A two-MeV He+ beam focused to a submicron spot is used in these CCM measurements to obtain both lateral and depth-resolved information on the cross hatch features observed and their association with a slight lattice tilt.

Diffusion barrier properties of ionized metal plasma deposited tantalum nitride thin films between copper and silicon dioxide

Tantalum nitride thin films with different thickness are sputtered deposited on silicon dioxide in the Cu/TaN/SiO2/Si multiplayer structure. Using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectroscopy, this work examines the impact of varying layer thickness on the crystal structure, resistivity, intermixing and reactions at the interfaces before and after annealing. The thinner the film thickness of TaN, the severe the reactions at the interface of Cu/TaN and consumed more conductive Cu. All the structures shown similar degradation process, and were found to be stable up to 500°C for 35 min. Accelerated grain growth and agglomeration were also observed after annealing temperature higher than 550°C at all Cu surfaces of the samples.

Study on SiNx passivated Cu/Ta/SiO2/Si multilayer structure

Silicon nitride (SiNx) thin film layers were deposited on Cu/Ta/SiO2/Si multilayer structures by Plasma Enhanced Chemical Vapor Deposition at the temperature 285°C. The influence of post deposition thermal annealing treatments on the micro-structural, compositional and thermal stability study of SiNx/Cu/Ta/SiO2/Si multilayer structure was studied and compared with unpassivated, Cu/Ta/SiO2/Si multilayer structure. It was found that after SiNx passivation, the formation of Cu2O and Ta2O5 was significantly reduced and the structure becomes more stable than unpassivated one. The reaction between Cu, Ta and O was not found in this SiNx/Cu/Ta/SiO2/Si multiplayer structure but the out diffusion of Ta to the Cu surface was unable to be suppressed. The Ta barrier was observed to fail at temperatures above 750°C due to the formation of TaxNy, at the interface of SiNx/Cu.

Micro-RBS study of nickel silicide formation

Abstract Two MeV He+ microbeam-Rutherford backscattering (μ-RBS) is used to obtain information on silicide formation in patterned nickel silicide samples under different annealing conditions. It is important to characterize silicide formation processes in such laterally non-homogenous samples in order to understand resistivity variations that are observed when metal oxide silicon field effect transistor (MOSFET) gate lengths are reduced, and when silicidation temperatures are changed. The patterned samples investigated consist of an array of square pads ( 70×70 μm 2 ) of the structure Ni(Pt)Six/Poly-Si (2000 A)/SiO2 (2500 A)/Si and narrow lines of 100 μm length and linewidths of 5 and 2 μm. μ-RBS (∼ 5 μm 2 beam spot) was used to obtain the thickness and stoichiometry of the silicide films for the square pads. The beam was focused to submicron dimensions for the scans over the narrow lines. μ-RBS results for the different silicide structures are presented and correlated with micro-Raman data.

Characterization of thick graded Si1 xGex/Si layers grown by low energy plasma enhanced chemical vapour deposition

Thick, linearly graded-composition strained Si1� xGex/Si layers were recently developed for proton beam bending and extraction experiments. Such unrelaxed layers which are many microns thick necessitate a low maximum germanium content. Here, graded Si1� xGex epilayers, 5–20 lm thick with maximum Ge compositions of x ¼ 0:5–1.7%, grown by low energy plasma enhanced chemical vapour deposition were characterized using a recently developed mode of ion channeling analysis which is capable of quantifying the small lattice rotations along off-normal planar directions. Highquality 10 l mS i 1� xGex epilayers with bend angles along off-normal directions which agree very well with those of fully strained layers are successfully grown.