Plasma Oxynitridation Research Articles

Characteristics of silicon oxynitride films grown by using neutral-beams and inductively coupled plasma

The characteristics of silicon oxynitride (SiON) films grown using neutral-beam and typical plasma-enhanced chemical vapor deposition methods are compared. Neutral-beam and plasma oxynitridation processes were performed using a nitrogen neutral beam at room temperature and a nitrogen plasma at 400°C, respectively, using the same deposition system. The neutral beam was generated via the surface neutralization of the ions produced by the inductively coupled plasma. The physical and electrical properties were measured using metal-insulator‑silicon structures. The plasma SiON films showed significant plasma-induced damage, while we demonstrate that the neutral beam method is suitable for growing SiON films at room temperature without plasma-induced damage or a high thermal budget.

TiN/titanium–aluminum oxynitride/Si as new gate structure for 3D MOS technology

Titanium-aluminum oxynitride (TAON) has been used as high-k gate dielectric for planar MOS devices (capacitors and transistors) and obtained by Ti/Al e-beam evaporation, with additional electron cyclotron resonance (ECR) plasma oxynitridation on Si substrates. Thus, planar MOS (Al/TAON/Si) capacitors were characterized by TEM and EDS analyses, and the film formation with thickness of 6.7nm and with Ti, Al, O and N into the TAON dielectric bulk is confirmed. However, for future 3D device technology application, these films have been not investigated. So, 3D MOS capacitors with Al/TAON/Si (as control sample) and TiN/TAON/Si gate structures for 3D technology were fabricated. Al/TAON and TiN/TAON layers on 3D gate region must present conformal coverage, which is a mandatory requirement for 3D transistors, such as FinFET. To characterize the TAON conformal coverage for this technology, the gate structure formed by Al/TAON/Si for FinFETs were fabricated and the ''Fin'' structures were obtained using a Focused Ion Beam (FIB) system to become thinner the width of active area to get the ''Fin'' structure. C-V curves of these structures were performed at 1MHz, and the three C-V curve regions (accumulation, depletion and inversion) are well defined for all capacitors, indicating that the conformal coverage on the 3D and FinFET gate regions can be occurred. Furthermore, these results indicated that TiN/TAON layers can be used as a new alternative for 3D MOS structures.

Titanium–aluminum oxynitride (TAON) as high- k gate dielectric for sub-32 nm CMOS technology

High- k insulators for the next generation (sub-32 nm CMOS (complementary metal–oxide–semiconductor) technology), such as titanium–aluminum oxynitride (TAON) and titanium–aluminum oxide (TAO), have been obtained by Ti/Al e-beam evaporation, with additional electron cyclotron resonance (ECR) plasma oxynitridation and oxidation on Si substrates, respectively. Physical thickness values between 5.7 and 6.3 nm were determined by ellipsometry. These films were used as gate insulators in MOS capacitors fabricated with Al electrodes, and they were used to obtain capacitance–voltage ( C– V) measurements. A relative dielectric constant of 3.9 was adopted to extract the equivalent oxide thickness (EOT) of films from C– V curves under strong accumulation condition, resulting in values between 1.5 and 1.1 nm, and effective charge densities of about 10 11 cm −2. Because of these results, nMOSFETs with Al gate electrode and TAON gate dielectric were fabricated and characterized by current–voltage ( I– V) curves. From these nMOSFETs electrical characteristics, a sub-threshold slope of 80 mV/dec and an EOT of 0.87 nm were obtained. These results indicate that the obtained TAON film is a suitable gate insulator for the next generation (MOS) devices.

High-k Gate-Dielectrics Based on Titanium-Aluminum for Sub-32 Nm CMOS Technology

High k insulators for the next generation (sub-32 nm CMOS (complementary metal-oxide-semiconductor) technology), such as titanium-aluminum oxynitride (TiwAlxOyNz) and titanium-aluminum oxide (TiwAlxOy), have been obtained by Ti/Al e-beam evaporation, with additional electron cyclotron resonance (ECR) plasma oxynitridation and oxidation on Si substrates, respectively. The physical thickness values between 5.7 nm and 6.3 nm were determined by ellipsometry. These films have been used as gate insulators in MOS capacitors, which were fabricated with Al electrodes and final sintering time at 4500C for 10 min in forming gas. These capacitors were used to obtain capacitance-voltage (C-V) measurements. A relative dielectric constant of 3.9 was adopted to extract the Equivalent Oxide Thickness of films from C-V curves under strong accumulation condition, resulting in values between 1.9 and 1.7 nm, and the effective charge densities of about 1011 cm-2. These results indicate that the obtained TiwAlxOyNz and TiwAlxOy films are suitable gate insulators for the next generation (MOS) devices.

Very Low Bit Error Rate in Flash Memory Using Tunnel Dielectrics Formed by Kr/O2/NO Plasma Oxynitridation

The gate leakage current which influences the charge hold time of flash memories is characterized as very localized in tunnel oxide area. And the leakage current value is relatively low as the quantity of the current. In conventional test-element-group (TEG) for evaluation of this leakage current, the gate leakage current is measured in relatively large area capacitors or transistors, as a result, the localized and low gate leakage current cannot be measured. In this paper, we propose the new concept TEG in which the localized gate leakage current corresponding to the bit error in the flash memory can be measured in short time. We statistically evaluated the stress induced leakage current (SILC) of all cells in very low gate leakage current region (about 10-16 A) in the very short time (a few seconds) and easily confirmed and categorized the localized cells with the large SILC after the stress. In addition, we show that plasma oxynitridation using Kr/O2/NO gases is effective in suppressing the anomalous SILC and carrier traps by statistically evaluation of 60,000 cells in proposed array TEG.

Electrical properties of ultra-thin oxynitrided layer using N 2O plasma in inductively coupled plasma chemical vapor deposition for non-volatile memory on glass

In this work, the silicon oxynitride layer was studied as a tunneling layer for non-volatile memory application by fabricating low temperature polysilicon thin film transistors on glass. Silicon wafers were oxynitrided by only nitrous oxide plasma under different radio frequency powers and plasma treatment times. Plasma oxynitridation was performed in RF plasma using inductively coupled plasma chemical vapor deposition. The X-ray energy dispersive spectroscopy was employed to analyze the atomic concentration ratio of nitrogen/oxygen in oxynitride layer. The oxynitrided layer formed under radio frequency power of 150 W and substrate temperature of 623 K was found to contain the atomic concentration ratio of nitrogen/oxygen as high as 1.57. The advantage of high nitrogen concentration in silicon oxide layer formed by using nitrous oxide plasma was investigated by capacitance–voltage measurement. The analysis of capacitance–voltage characteristics demonstrated that the ultra-thin oxynitride layers of 2 nm thickness formed by only nitrous oxide plasma have good properties as tunneling layer for non-volatile memory device.

Influence of pre-deposition treatments on the interfacial and electrical characteristics of ZrO 2 gate dielectrics

ZrO 2 films are deposited on bare silicon, silicon with a pre-sputtered ultrathin Zr metal layer, and plasma oxynitrided Si surface by reactive sputtering and the growth of interface layer between ZrO 2 and Si is investigated. The ZrO 2/Si dielectric stacks, before and after annealing in oxygen ambient, are characterized by grazing incident angle X-ray diffraction, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, capacitance–voltage and current–voltage measurements. The results reveal that as-deposited ZrO 2 films contain nanocrystallites embedded in the amorphous matrix. ZrO 2 films deposited on an ultrathin Zr metal layer show a thinner interface layer but contain a greater amount of oxide traps. ZrO 2 films deposited on SiO x N y grown by NH 3 plasma oxynitridation are found to retard the growth of the interface layer effectively, and they also exhibit fewer oxide traps and lower leakage currents.

Comparison of Thermal Stability and Chemical Bonding Configurations of Plasma Oxynitrided Hf and Zr Thin Films

In this work, we study the characteristics of plasma oxynitrided Hf and Zr thin films. A 5-nm-thick Hf or Zr metal film is deposited on the bare Si substrate, followed by plasma oxynitridation on these metal films in a or ambient. Incorporation of O and N leads to the formation of and films. The high nitrogen content in the films prepared by plasma oxynitridation is found to increase the onset of the crystallization temperature, as compared to films prepared by plasma oxynitridation. Nevertheless, the difference in crystallization temperature is not seen for films. The interlayer (IL) between (or ) and Si is found to be thinner for the films with plasma oxynitridation than those with plasma oxynitridation. However, the nitrogen incorporated by plasma oxynitridation appears to be depleted after rapid thermal oxidation annealing and is not effective to inhibit the growth of the IL. The activation energy of the IL growth for and oxynitrided is 0.23 and 0.13 eV, respectively. The activation energy of the IL growth for and oxynitrided is 0.19 and 0.14 eV, respectively.

Investigation of plasma oxynitridation of Si(001) by NH 3/N 2O/Ar remote plasma processing

Plasma oxynitridation of Si(001) was carried out by NH 3/N 2O/Ar remote plasma generated from a toroidal-type remote plasma source in a commercial 8-in. plasma-enhanced chemical vapor deposition (PECVD) system. Oxynitridation experiments of Si were performed by varying the NH 3/N 2O/Ar gas flow ratio and plasma exposure time at the substrate temperature of 500 °C. Time evolution of the layer thickness, chemical composition, and bonding characteristics of the silicon oxynitride layers were investigated by various analytical methods including X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and high-resolution transmission electron microscopy (HR-TEM). The results showed a formation of the silicon oxynitride layers with the film thickness of 1.5–2.0 nm and different compositions depending on the experimental conditions. N content incorporated in the silicon oxynitride increases but the growth rate of silicon oxynitride layer decreases with increasing NH 3/N 2O gas flow ratio.

Spin-dependent tunneling junctions with AlN and AlON barriers

We report on ferromagnetic spin-dependent tunneling (SDT) junctions with NiFe/AlN/NiFe and NiFe/AlON/NiFe structures. Good barriers were formed by plasma nitridation and oxy-nitridation of Al films. Tunneling magnetoresistance ratios (TMR) up to 18% were observed at room temperature. The devices exhibit lower resistance-area products than those seen in reference junctions with Al2O3 barriers. The degradation in TMR at higher bias voltages is found to be less than that found in standard alumina junctions. AlN and AlON could thus be alternate materials for the tunnel barrier in SDT junctions.

Formation of ultrathin oxynitride layers on Si(100) by low-temperature electron cyclotron resonance N2O plasma oxynitridation process

We have undertaken the characterization of the low-temperature direct electron cyclotron resonance (ECR) N2O plasma process on the technically important Si(100) surface by the combined use of the newly developed ultrahigh vacuum (UHV)-based contactless capacitance–voltage (C–V) and x-ray photoelectron spectroscopy (XPS) techniques. An UHV-based contactless C–V measurement system allowed for the first time a direct in situ assessment of electronic properties of “free” Si surfaces and the surfaces covered with an ultrathin insulator layer. The UHV contactless C–V analysis indicated that a oxynitride/Si interface with a minimum interface state density of 1×1011 eV−1 cm−2 could be realized by the ECR N2O oxynitridation process at 400 °C. The angle-resolved XPS study showed that the formation of a phase-separated Si3N4/SiO2 structure is important to realize such a interface at low temperatures. The electronic and the chemical properties of the interfaces were found to be strongly correlated.