A. M. Mahajan

Sol–gel deposited ceria thin films as gate dielectric for CMOS technology

In this work, cerium oxide thin films were prepared using cerium chloride heptahydrate, ethanol and citric acid as an additive by sol–gel spin-coating technique and further characterized to study the various properties. Chemical composition of deposited films has been analysed by FTIR which shows existence of CeO2. The samples have been optically characterized using ellipsometry to find refractive index of 2·18 and physical thickness which is measured to be 5·56 nm. MOS capacitors were fabricated by depositing aluminum (Al) metal using the thermal evaporation technique on the top of CeO2 thin films. Capacitance–voltage measurement was carried out to calculate the dielectric constant, flat-band voltage shift of 18·92, 0·3–0·5 V, respectively and conductance–voltage study was carried out to determine the Dit of 1·40 × 1013 eV − 1 cm − 2 at 1 MHz.

Electrical properties of MOS capacitors formed by PEALD grown Al2O3 on silicon

In the present work, we have grown 2.83 nm thin Al2O3 films directly on pre-cleaned p-Si (100) substrate using precursor Trimethyl Aluminium (TMA) with substrate temperature of 300°C in a Plasma Enhanced Atomic Layer Deposition (PEALD) chamber. The MOS capacitors were fabricated by depositing Pt/Ti metal bilayer through shadow mask on Al2O3 high-k by electron beam evaporation system. The MOS devices were characterized to evaluate the electrical properties using a capacitance voltage (CV) set-up. The dielectric constant calculated through the CV analysis is 8.32 for Al2O3 resulting in the equivalent oxide thickness (EOT) of 1.32 nm. The flat-band shift of 0.3 V is observed in the CV curve. This slight positive shift in flat-band voltage is due to the presence of some negative trap charges in Pt/Ti/ALD-Al2O3/p-Si MOS capacitor. The low leakage current density of 3.08 × 10−10 A/cm2 is observed in the JV curve at 1 V. The Si/Al2O3 barrier height ΦB and the value of JFN are calculated to be 2.78 eV and 3.4 × 10−5 A/cm2 respectively.

High Dielectric Constant ZrO2 Films by Atomic Layer Deposition Technique on Germanium Substrates

Germanium has been reconsidered as a potential substitute channel material for high-performance MOSFETs due to its intrinsic high mobilities for both electrons (3900 cm2 s-1V-1) and holes (1900 cm2 s-1V-1). In the present work we have fabricated Pt/Ti metal bilayered ALD-ZrO 2/n-Ge based MOS capacitors. The ZrO2 thin film was deposited on n-Ge (100) substrates by using ZrEMA and oxygen precursors at 300 °C in a PEALD system. The Pt/Ti bilayer metallization was carried out using e-beam evaporation and PMA using a RTA system at 350 °C in the forming gas. The thickness of the ZrO2 gate stack was measured to be 3.61 nm using an ellipsometer. The electrical study was done by analyzing capacitance voltage and current voltage measurements. The flat-band shift was found to be 0.22 V, Qeff was 3.55×1012 cm-2 and Dit was 8.53×1012 cm-2 eV-1. Current voltage characteristics have been analyzed to know the conduction mechanism in fabricated MOS devices.

ANALYSIS OF CAPACITANCE ACROSS INTERCONNECTS OF LOW-K DIELECTRIC USED IN A DEEP SUB-MICRON CMOS TECHNOLOGY

The paper presents the detailed analysis of the intercon- nect capacitance, crosstalk time and peak crosstalk voltage. The de- pendency of the couple capacitance and fringe capacitance on the in- terconnect layer dimensions affects significantly to the interconnect ca- pacitance. The peak crosstalk time obtained to be 13 femtoseconds for 9.6 femtoseconds of propagation delay, while the maximum crosstalk voltage obtained to be 178 mV.

Electronic nose: A toxic gas sensor by polyaniline thin film conducting polymer

This paper presents study of toxic gas sensing property by polyaniline thin film conducting polymer for ammonia gas. In this work, the precipitate of the conducting polymer has been synthesized by chemical method. The conducting polymer film which acts as an active layer of sensor was prepared with the help of the precipitate (of the conducting polymer) by spin-coating technique. The deposited films were characterized by FTIR spectroscopy and four probe method. The study indicates that, the resistance of the film decreases with the increase in concentration of ammonia at the known volume.

Growth and Characterization of SiO2 Films for the Fabrication of Optical Waveguides

The SiO2 films grown by Plasma Enhanced Chemical Vapor Deposition (PECVD) system are used for the fabrication of optical waveguides due to their several advantages such as low temperature deposition, controlled refractive index and low tensile stress. These films are preferably used as core and cladding layers in the waveguide. The waveguides formed by the films with controlled refractive index are found to be most suitable for the coupling with the optical fibers as the R.I. are in the range of 1.45 to 1.47. It has been found from the observations that the SiO2 film grown at 300° C shows the excellent properties i.e. better thickness, precisely controlled refractive index and comparatively low tensile stress. The present paper reports the study of the deposition of SiO2 films with indigenously developed PECVD system and their characterization.

Monomer methylmethacrylate (MMA) incorporated hybrid low-k thin films

Low-dielectric-constant hybrid thin films were deposited by sol-gel spin coating technique, using methyl methacrylate and tetraethyl orthosilicate as organic and inorganic precursors, respectively. The deposited hybrid thin films were annealed at different temperatures in the range 200°C–500°C. Fourier transform infrared spectroscopic study reveals the presence of Si-O-Si and C=C bonds, which confirms the successful assimilation of carbon in the deposited hybrid thin film. The carbon incorporation is responsible for lowering the dielectric constant (k) in the deposited film. The k value was determined to be 2.51, as measured from the highfrequency capacitance-voltage curve. This is a significant contribution, since the deposition method did not involve polymerization. The electrical characteristics, such as border trap charge, interface trap density, and fixed oxide charge were estimated to be 4.10 × 1015 cm−2, 1.94 × 1011 cm−2 eV−1, and 1015 cm−2, respectively, indicating the optimum annealing temperature to be 200°C.

Investigation of Current Conduction Mechanism in HfO2 Thin Film on Silicon Substrate

In this work, we have investigated current conduction mechanisms in HfO2 thin film deposited on silicon substrate by RF sputtering technique. The thin films of HfO2 were deposited on p-type silicon substrates. FTIR measurement shows the presence of hafnium in the film. Among the various conduction mechanisms the 13.7 nm thin HfO2 film on Si follows the Fowler–Nordheim (FN) tunneling. The Poole–Frenkel (PF) emission, Schottky emission (SE) and Direct Tunneling (DT) also studied. The barrier height (ϕB) of 0.74 eV is calculated from experimental work through Fowler–Nordheim tunneling mechanism.

Capacitance-Voltage Measurement of SiO2/GeOxNy Gate Stack on Surface Passivated Germanium

Germanium (Ge) based MOS transistors is possible alternative to silicon based MOS transistors due to high mobility of carriers in Ge. Extensive research is going on for fabrication of high mobility MOS devices worldwide. Here, we have studied the c-v characteristics of Ge based surface passivated MOS structure such as dielectric constant of gate stack, effective oxide charges, density of interface charges at semiconductor oxide interface etc. The interface trap density extracted from the C-V/G-V measurement showed the lowest interface trap density of 7.82 × 1011 cm2 eV−1. The minimum leakage current density for SiO2/GexONy gate dielectric stack is 1.35 × 10−7 A cm−2 at gate bias of 1 V.

Amorphization of SiO2 Thin Films by Using 200 MeV Ag15+ Ions

Effect of swift heavy ions (SHI) on low-k SiO2 thin films has been investigated. SiO2 thin films were deposited on pre-cleaned p-Si substrate by using sol-gel spin coating technique. Further, deposited films were annealed at 400 ∘C to remove structural irregularities. Prepared samples were irradiated with 200 MeV Ag15+ ions at different ion fluence such as 5 × 1011, 1 × 1012 and 5 × 1012 ions/cm2. Deposition of SiO2 was confirmed by using EDAX and FTIR spectroscopy. Increase in ion fluence increases the RMS roughness from 1.49 to 7.79 nm. The transformation of deposited material from polycrystalline to amorphous nature was confirmed from XRD spectra. Increase in SHI fluence decreases the grain size from 181.3 to 74.1 nm for pristine and sample irradiated at 5 × 1011 ions/cm2. Whereas, for sample irradiated with 5 × 1011 ions/cm2 fluence doesn’t show crystalline peak at (011). It is observed that SHI irradiation leads to grain agglomeration with decrease in crystal size at higher fluence. Further, conductivity of the samples under study was observed to be decreased with increase in ion fluence. Thus, it is demonstrated that the surface and structural properties of low-k silica thin films can be tailored by controlling the SHI fluence.