Metal Oxide Silicon Capacitors Research Articles

Electronic detection of surface plasmon polaritons by metal-oxide-silicon capacitor

An electronic detector of surface plasmon polaritons (SPPs) is reported. SPPs optically excited on a metal surface using a prism coupler are detected by using a close-coupled metal-oxide-silicon (MOS) capacitor. Incidence-angle dependence is explained by Fresnel transmittance calculations, which also are used to investigate the dependence of photo-response on structure dimensions. Electrodynamic simulations agree with theory and experiment and additionally provide spatial intensity distributions on and off the SPP excitation resonance. Experimental dependence of the photoresponse on substrate carrier type, carrier concentration, and back-contact biasing is qualitatively explained by simple theory of MOS capacitors.

Growth characteristics and electrical properties of SiO2 thin films prepared using plasma-enhanced atomic layer deposition and chemical vapor deposition with an aminosilane precursor

The deposition of high-quality SiO2 films has been achieved through the use of both plasma-enhanced chemical vapor deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) methods using H2Si[N(C2H5)2]2 as a Si precursor. We systematically investigated growth characteristics, chemical compositions, and electrical properties of PE-CVD SiO2 prepared under various deposition conditions. The SiO2 films prepared using PE-CVD showed high purity and good stoichiometry with a dielectric constant of ~4. In addition, the PE-ALD process of the SiO2 films exhibited well-saturated and almost linear growth characteristics of ~1.3 A cycle−1 without notable incubation cycles, producing pure SiO2 films. Electrical characterization of metal-oxide silicon capacitor structures prepared with each SiO2 film showed that PE-ALD SiO2 films had relatively lower leakage currents than PE-CVD SiO2 films. This might be a result of the saturated surface reaction mechanism of PE-ALD, which allows a smooth surface in comparison with PE-CVD method. In addition, the dielectric properties of both SiO2 films were further evaluated in the structures of In–Ga–Zn–O thin-film transistors, and they both showed good device performances in terms of high I on − I off ratios (>108) and low off-currents (<10−11 A). However, based on the negative bias stress reliability test, it was found that PE-ALD SiO2 showed better reliability against a negative V th shift than PE-CVD SiO2, which might also be understood from its smoother channel/insulator interface generation at the interface.

Gamma and proton irradiation effects and thermal stability of electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al2O3 dielectric

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al2O3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al2O3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance–voltage and current–voltage characteristics under gamma and proton irradiations up to equivalent doses of 30Mrad and 21.07Mrad, respectively. While similar negative charge densities are initially extracted for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H2O instead of O3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H2O-grown Al2O3 layers may explain their higher radiation resistance. Finally, irradiated and non-irradiated MOS capacitors with differently processed Al2O3 layers have been subjected to thermal treatments in air at temperatures ranging between 100°C and 200°C and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O3-grown MOS structures. This can be explained by a trapped holes emission process, for which an activation energy of 1.38±0.15eV has been extracted.

Advanced PVD TiN for Metal Gate Application

High-κ metal gate is widely used for 32nm and beyond to enable scaling down of MOSFET geometry while improving device speed and gate leakage. This structure requires a good work function metal to tune Vt as well as a stable metal barrier to control inter-diffusion and interaction between the multiple metal gate layers. To meet the integration requirements of metal gate, it is very important to choose the proper metal thin film process. Its stability and excellent integration performance make TiN a good option for metal gate application, but the traditional PVD (physical vapor deposition) TiN process still faces issues, such as plasma damage and poor gap-fill capability. RFPVD (radio frequency physical vapor deposition) TiN has been developed for metal gate application. This paper presents studies of the film texture, density, and inter-diffusion base on different metal gate layers. MOSCAP (metal oxide silicon capacitor) tests showed that RF PVD TiN exhibits low Dit and device leakage. To meet the strict gap-fill requirement of the gate-last scheme, physical gap-fill performance of the high-pressure RF TiN process was checked. It achieved more than 60% bottom coverage and minimal sidewall coverage, allowing the electrode gap-fill window to be effectively enlarged.

A model to describe the humplike feature observed in the accumulation branch of capacitance-voltage characteristics of MOS capacitors with oxide-hosted silicon nanoparticles

A model is proposed for description of a humplike feature that was previously observed in the lowfrequency capacitance-voltage (C-U) characteristics of MOS capacitors with oxide layers containing silicon nanoparticles. The formation of this feature is related to variation (at the frequency of measurements) of a charge accumulated in the oxide due to injection of charge carriers from electrodes and their migration by tunneling through oxide along linear chains formed by Si nanoparticles (with a certain spread of tunneling distances in the chain). The adequacy of the model is illustrated with the simple example of metal-oxidesilicon (MOS) capacitor with a planar array of Si nanoparticles in the oxide and a monopolar injection of holes from the accumulation layer of the p-type semiconductor. A C-U curve measured on an MOS capacitor with amorphous Si clusters is presented, which closely resembles curves with a two-hump feature predicted by the proposed model.

2 MeV electron irradiation effects on the electrical characteristics of metal–oxide–silicon capacitors with atomic layer deposited Al2O3, HfO2 and nanolaminated dielectrics

The effects of 2MeV electron irradiation on the electrical characteristics of atomic layer deposited (ALD) high permittivity (high-k) layers of Al2O3, HfO2 and a nanolaminate of them are evaluated. Metal–oxide–semiconductor capacitors with a nominal dielectric physical thickness of 10nm were fabricated on different p-type and n-type silicon substrates. The capacitance–voltage (C–V) and current–voltage (I–V) characteristics of the different structures are analyzed as a function of electron irradiation. A progressive negative shift of the C–V characteristics is observed with increasing electron irradiation, indicating the generation of effective positive charges. Similar generation rates for effective trapped charges and interface states are obtained for all the different high-k dielectric layers studied. The hysteresis of the C–V curves after irradiation increases in the case of Al2O3 samples, for HfO2 decreases while the irradiation has little impact on the hysteresis of the nanolaminate stack. A progressive increase of the leakage current with electron irradiation dose is observed for all the studied dielectrics. The analysis of the current–voltage characteristics measured at different temperatures point to Poole–Frenkel as the dominant conduction mechanism. Under the studied conditions, no impact of electron irradiation fluence on dielectric breakdown voltage has been appreciated.

Structural, optical and electrical properties of high-k ZrO2 dielectrics on Si prepared by plasma assisted pulsed laser deposition

ZrO2 films were grown on p-type Si(100) using plasma assisted pulsed laser deposition and the electrical characteristics of the ZrO2 dielectrics incorporated in metal oxide silicon (MOS) capacitors were studied in combination with their structural and optical properties. The ZrO2 dielectric layers are of polycrystalline structure with a monoclinic phase and show good interfacial properties without obvious SiOx interface. The electrical performance of the capacitors exhibits typical MOS-type capacitance–voltage (C–V) and leakage current density–voltage (J–V) characteristics. Thermal annealing of the ZrO2 dielectrics results in an improvement in C–V and J–V characteristics and a reduction in C–V hysteresis without obvious introduction of leakage paths for the fabricated MOS capacitors. The dielectric constant was calculated to be 15.4 and the leakage current density was measured to be 6.7×10−6A/cm2 at a gate voltage of +1.0V for 900°C annealed ZrO2 dielectric layers with an equivalent oxide thickness of 5.2nm.

Optical, dielectric and morphological studies of sol–gel derived nanocrystalline TiO 2 films

Nanocrystalline TiO 2 films have been synthesized on glass and silicon substrates by sol–gel technique. The films have been characterized with optical reflectance/transmittance in the wavelength range 300–1000 nm and the optical constants ( n, k) were estimated by using envelope technique as well as spectroscopic ellipsometry. Morphological studies have been carried out using atomic force microscope (AFM). Metal-Oxide-Silicon (MOS) capacitor was fabricated using conducting coating on TiO 2 film deposited on silicon. The C– V measurements show that the film annealed at 300 °C has a dielectric constant of 19.80. The high percentage of transmittance, low surface roughness and high dielectric constant suggests that it can be used as an efficient anti-reflection coating on silicon and other optical coating applications and also as a MOS capacitor.

Effects of Applied Mechanical Uniaxial and Biaxial Tensile Strain on the Flatband Voltage of (001), (110), and (111) Metal–Oxide–Silicon Capacitors

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The flatband-voltage shift of metal–oxide–silicon capacitors is investigated under the application of low-level stress (up to 220 MPa of biaxial stress and 380 MPa of uniaxial stress) to different substrate orientations. We propose that the flatband-voltage shift be modeled as the net effect of silicon-band-edge shifts and modulation of the separation between the band edge and the Fermi level under low levels of applied mechanical strain. For the (001) n-type substrate, a negative flatband-voltage shift is observed due mainly to the downward shift of the conduction-band edge, while a positive flatband-voltage shift is observed for the (001) p-type substrate due to the upward shift of the valence-band edge. For the uniaxial tensile strain on n-substrate capacitors for (110) and (111) substrates, the modulation of band-edge and Fermi-level separation by the conduction-band density of states exceeds the downward shift of the conduction band, which induces a positive flatband shift that is distinct from that observed in the (001) n-substrate. The shift of the band edges is determined by the proposed model and compared with theoretical calculations. </para>

Rare Earth Ion Implantation for Silicon Based Light Emission

Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were formed in the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). Efficient electroluminescence was obtained for the wavelength range from UV to infrared with a transparent top electrode made of indium-tin oxide. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies distinctly above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Finally, application aspects to the field of biosensing will be shown.

An aluminum-gate metal-oxide-silicon capacitor with a tunnel-thin oxide under the bidirectional electric stress

Bidirectional electric stresses are performed in metal—oxide—silicon capacitors with ultrathin (2.5 nm) oxides and with highly doped substrates. The observed effects are compared to those occurring under the conventional unidirectional constant-current overload. The effects observed after stress of ultrathin oxides bring into play defects of comparable nature to those noted for thick oxides, namely, neutral traps. Furthermore, soft breakdown events are scrutinized based on defect creation throughout the oxide and modulation of charge state trapping at the interfaces.

Physical and Electrical Characteristics of HfO2 Gate Dielectrics Deposited by ALD and MOCVD

Film characteristics of gate dielectrics formed on Si(100) by atomic layer deposition (ALD) or metallorganic chemical vapor deposition (MOCVD) were investigated by atomic force microscopy, transmission electron microscopy, secondary ion mass spectroscopy (SIMS), X-ray reflectometry, ellipsometry, and electrical measurements. and water were the precursors used for ALD deposition at 300 and 370°C, whereas was used for MOCVD deposition at 550 and 650°C. Film thickness increases linearly with time for both deposition techniques. The ALD and MOCVD films have comparable density. MOCVD thin films are polycrystalline, while the 300°C deposited ALD are amorphous. The 370°C deposited ALD are polycrystalline. SIMS analysis indicated chlorine and carbon are the major contaminants in ALD and MOCVD films, respectively. Electrical properties of ALD and MOCVD films were examined using metal oxide silicon capacitors. Well-behaved capacitance-voltage and leakage current-voltage characteristics were obtained for both types of films. ALD films have slightly higher capacitance and comparable leakage when compared to MOCVD films. Room temperature and 105°C stressing of the capacitance-voltage curves showed a significant shift in the capacitance-voltage curve indicating that charge trapping was observed for all films with the 650°C deposited MOCVD showing the largest capacitance-voltage shift. Unlike MOCVD films, the capacitance-voltage characteristics of ALD films remain well behaved after stressing. © 2005 The Electrochemical Society. All rights reserved.

Rare Earth Ion Implantation for Silicon Based Light Emission: From Infrared to Ultraviolet

AbstractUsing ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were incorporated into the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). The silicon dioxide layer did not contain silicon nanoclusters. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. The electroluminescence properties were studied with respect to the luminescence spectra, decay time, impact excitation, cross relaxation (Tb3+), and power efficiency. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies well above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Moreover, we demonstrate photo- and electroluminescence in correlation to charge trapping characteristics for Er-rich MOSLEDs with a varying silicon cluster content. Finally, application aspects to the field of biosensing will be discussed.

Investigation of the electrical degradation of a metal–oxide–silicon capacitor by scanning thermal microscopy

A scanning thermal microscope is used to study the temperature distribution on the gate surface of a MOS structure submitted to an electric stress. Over a threshold of stress current intensity, hot spots have been observed and then numbered versus stress conditions. The data analysis shows that the hot spots number depends on injected current and also on the MOS structure degradation history. The temperature map of the gate surface is riddled with hot spots since the sample breakdown. Otherwise, hot spots seem to appear in privileged areas like the gate borders. On the basis of the literature, our observations lead us to conclude that hot spots result of degradations inside the structure.

Intrinsic Gettering in Nitrogen-Doped and Hydrogen-Annealed Czochralski-Grown Silicon Wafers

The properties of nitrogen-doped and hydrogen-annealed Czochralski-grown silicon (NHA-CZ-Si) wafers were investigated in this study. The quality of the subsurface was investigated by monitoring the generation lifetime of minority carriers, as measured by the capacitance-time measurements of a metal oxide silicon capacitor (MOS C-t). The intrinsic gettering (IG) ability was investigated by determining the nickel concentration on the surface and in the subsurface as measured by graphite furnace atomic absorption spectrometry (GFAAS) after the wafer was deliberately contaminated with nickel. From the results obtained, the generation lifetimes of these NHA-CZ-Si wafers were determined to be almost the same as, or a little longer than those of epitaxial wafers, and the IG ability was proportional to the total volume of oxygen precipitates [i.e., bulk micro defects (BMDs)], which was influenced by the oxygen and nitrogen concentrations in the wafers. Therefore, it is suggested that the subsurface of the NHA-CZ-Si wafers is of good quality and the IG capacity is controllable by the nitrogen and oxygen concentrations in the wafers.

The electrical and material properties of MOS capacitors with electrolessly deposited integrated copper gate

The electrical properties of electroless-deposited barriers were studied using metal-oxide-silicon (MOS) capacitors with thin (14 nm) thermal oxide. Three different metal electrodes were deposited on a thin sputtered Co seed layer: (a) sputtered Al, (b) electroless Co(W,P) and (c) electroless multilayer of Co(W,P)/Cu/Co(W,P). The study includes thermal stress in vacuum in the 300–600°C temperature range, for periods of 30 min to 4 h, followed by electrical characterization. The high-frequency capacitance versus voltage ( C– V) characteristics of the capacitors was near ideal after annealing at 300–500°C for 30 min. After annealing at higher temperatures for longer times the inversion capacitance increased above the ideal high-frequency value while the flat band voltage remained unchanged. The minority carrier lifetime, as obtained from transient capacitance analysis, was in the range of 60 μs for samples annealed at temperatures below 500°C. It dropped for the samples with copper layers to 12 μs after 520°C anneal for 2 h and to 1 μs after 600°C for 4 h while remaining in the range of 50–60 μs for the samples with either electroless barrier or aluminum. AES profiling indicated that the copper profile remained unchanged after annealing at temperatures up to 500°C anneal for 30 min. Above 520°C, the copper profile showed significant diffusion onto the Co(W,P) barrier layer underneath and much less diffusion onto the Co(W,P) capping layer above.

Electric bidirectional stress effects on metal–oxide–silicon capacitors

Bidirectional electron injections were performed in thick and thin oxides of metal–oxide–silicon capacitors under a constant oxide electric field. Results show that dissymmetry, due to electron trapping near both oxide interfaces, is accentuated when the oxide is thin. However electron trapping is more marked when oxide is thick. Two kinds of thick oxide were used: wet and dry technologies. Wet oxide contains relatively more defects than dry. This is due to hydrogen incorporation in wet oxide during the oxidation process. But this difference is not well marked, because boron atoms injected after the oxidation process would deactivate hydrogen atoms. We describe the electron trapping by a well-known power law. The exponent of this law depends on oxide field polarity and also on oxide thickness but is technology independent. Results also show a nonexpecting behavior of tunneling current during bidirectional stress at a constant voltage. Here, we describe its causes and effects.

Positive charge instability during bidirectional stress on metal–oxide–silicon capacitors

Bidirectional electron injections are made on metal–oxide–silicon capacitors under constant currents or constant voltages. It is shown that both stresses reveal the same generation mechanism of oxide defects and consequently confirm that the gate/oxide interface is more stress resistant than the oxide/silicon interface. It is also shown that the created positive charge is unstable during bidirectional stress. We characterize this instability by studying dielectric defect neutralization following a new procedure. Oxide field intensity and polarity are considered as the principal precursors of this instability. Without any applied field, the neutralization follows a logarithmic law; while under a nonstressing field it follows an exponential law. Both kinetic laws are linked, since the logarithmic law describes the saturation value of the exponential one, and hence both describe the same process. Results of both current and voltage stresses give a power law between the oxide field near the cathode during stress and the capture cross section measured from neutralization kinetics.

Charge separation technique for metal–oxide–silicon capacitors in the presence of hydrogen deactivated dopants

An improved charge separation technique for metal–oxide–silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance–voltage measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps, and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with Co60 γ rays at 100 °C and zero bias, where the dopant deactivation is significant.

Relaxation of positive charge during bidirectional electric stress on metal–oxide–silicon capacitors

Relaxation phenomena of positive charges, created in a metal–oxide–silicon capacitor by bidirectional Fowler–Nordheim electron injections under constant current, have been studied and their kinetics have been quantitatively characterized. After creation, positive charges are neutralized under electron injections at constant current. The gate bias shift caused by the neutralization process has an exponential dependence on time during relaxation irrespective of stress field polarity and stress duration. Analysis of data assuming nonelectron detrapping gives capture cross section values in the range of 3.5–6.7×10−16 to 2.1×10−15 cm2. The compilation of data given in literature and our present results shows that the main responsible defect in the oxide is the amphoteric traps negatively charged near the cathode and positively charged near the anode.