D. K. Shih

Study of the SiO2/Si interface endurance property during rapid thermal nitridation and reoxidation processing

The effects of rapid thermal nitridation of oxides (RTN) and rapid thermal reoxidation of rapid thermal nitride oxides (RTO/RTN) on the SiO2/Si interface endurance property have been studied. It is found that in order to enhance the SixNyOz/Si interface ‘‘hardness’’ [i.e., less interface states (Dit) are generated during high electric field stress], an interfacial oxidation process during RTN or RTO/RTN must occur. This oxidation reaction not only removes the nitridation‐induced damages but also grows an interfacial strainless oxide. The existence of small amounts of nitrogen at the interface is responsible for the strainless oxide growth, and hence the improvement of SixNyOz/Si interface strength. A physical model based on these observations is described, which considers the generation of silicon and oxygen dangling bonds at the SixNyOz/Si interface during rapid thermal processing.

Metal‐oxide‐semiconductor characteristics of rapid thermal nitrided thin oxides

The electrical properties of thin nitrided oxide (∼100 A) formed by rapid thermal nitridation (RTN) in pure NH3 have been studied. It is found that the current‐voltage characteristic of RTN oxides follows a Fowler–Nordheim tunneling behavior with modifications caused by electron trapping processes at the oxide surface and interface. The trapping density is dependent on the RTN conditions. At the interface, both fixed charge (Nf) and interface state (Dit) densities exhibit turnaround phenomena when the RTN process proceeds. The maximum values of Nf and Dit at the turnaround points are lower for the higher temperature RTN, suggesting a viscous flow related strain relieving mechanism associated with RTN of thin oxides. Films with superior endurance behavior (QBD=20.4 C/cm2 compared with QBD=5.1 C/cm2 of thermal oxide under 10 mA/cm2 constant current stress) have been obtained by RTN at 1000 °C, 10 s.

Charge trapping properties in thin oxynitride gate dielectrics prepared by rapid thermal processing

In this letter, effects of post‐nitridation anneals on charge trapping properties and charge‐to‐breakdown (Qbd) of thin (∼8.6 nm) rapidly thermal nitrided (RTN) gate SiO2 have been studied. Post‐nitridation anneals consist of either rapid thermal reoxidation (RTO) in pure O2 or rapid thermal anneal (RTA) in pure N2 ambient. Both the gate voltage shift (ΔVg) and flatband voltage shift (ΔVfb) have been used to characterize the charge trapping properties under Fowler–Nordheim electron injection. It is found that both RTO and RTA reduce ΔVfb and/or ΔVg resulting from the reduction of trapped electrons as well as high‐field stress‐induced positive charge generation. Positive charge generation resulting from either donor‐type interface state generation or trapped holes is discussed. Qbd of RTN SiO2 has been improved after RTO, and can be even larger than that of the thermal SiO2. RTA of RTN SiO2 in N2 also improves Qbd; however, the charge trapping behavior is different from that of RTO/RTN SiO2. The physical m...

Effects of post‐nitridation anneals on radiation hardness in rapid thermal nitrided gate oxides

Effects of post‐nitridation anneals on radiation hardness of metal‐oxide‐semiconductor (MOS) capacitors with rapid thermal nitrided (RTN) gate oxides have been studied. Post‐nitridation anneals consisted of either rapid thermal reoxidation (RTO) in pure O2 or rapid thermal anneals (RTA) in pure N2 ambient. The radiation was performed by exposing devices to x rays at doses of 0.5–5.0 Mrad (Si). Comparing RTO and RTA anneals at the same temperature and time for given nitrided oxides, it was found that RTO enhanced the radiation hardness while RTA in N2 had detrimental effects, in terms of interface‐state generation (ΔDit) and flatband voltage shift (ΔVfb). The strainless interfacial oxide regrowth during RTO of RTN oxides is responsible for the enhanced interface ‘‘hardness’’ of RTN/RTO oxides. A physical mechanism is described to account for the observation.

Stable, self‐aligned TiNxOy/TiSi2 contact formation for submicron device applications

The formation of the TiNxOy/TiSi2 bilayer on Si by rapid thermal nitridation of titanium silicide in NH3 has been studied. The chemical stability in dilute HF and the effectiveness of TiNxOy on TiSi2 as a diffusion barrier for Al are discussed. The results show that this bilayer has good chemical stability in dilute HF at least for 60 s and Al/TiNxOy/TiSi2/Si is thermally stable up to 500 °C for 30 min sintering.

Suppression of lateral Ti silicide growth by ion beam mixing and rapid thermal annealing

One of the most important issues in the self‐aligned silicide technology has been lateral silicide formation over the sidewall oxide spacers. In this work, the lateral silicide growth has been considerably suppressed by the use of ion beam mixing and rapid thermal annealing. Metal‐oxide‐semiconductor transistors fabricated using this technology show good electrical characteristics with negligible conduction between gate and source/drain electrodes.

Rapid thermal oxidation of thin nitride/oxide stacked layer

The effects of rapid thermal oxidation (RTO) on the chemical vapor deposited nitride/oxide layer for thin gate dielectrics were studied. Successful growth of a top oxide of ∼25 A was confirmed using x‐ray photoelectron spectroscopy and no punchthrough of the chemical vapor deposited nitride was observed for a nitride thickness of 60 A. Changes in electrical properties after RTO were studied using current‐voltage and charge‐to‐breakdown measurements. Results indicate that the top oxide reduces the leakage current under positive gate bias and increases the leakage current at high fields for negative gate bias. In addition, the charge to breakdown of the layer is increased after RTO.

Transconductance degradation and interface state generation in metal-oxide-semiconductor field-effect transistors with oxynitride gate dielectrics under hot-carrier stress

The hot‐carrier immunity of submicrometer (0.8 μm) n‐channel metal‐oxide‐semiconductor field‐effect transistors with thin (∼8.6 nm) oxynitride gate dielectrics prepared by rapid thermal reoxidation (RTO) of rapidly thermal nitrided (RTN) SiO2 has been studied. The hot‐carrier immunity was evaluated in terms of hot‐carrier‐induced transconductance degradation (ΔGm/Gm0) and interface state generation (ΔDit/Dit0) which was measured by using charge pumping current (Icp) measurement. It is found that for improved device performance and reliability, there exists an optimum RTO condition for a given RTN SiO2. In addition, a strong correlation between ΔDit/Dit0 and ΔGm/Gm0 has been observed.

Radiation effects in ultrathin nitrided oxides prepared by rapid thermal processing

The radiation hardness of metal‐oxide semiconductor capacitors with nitrided oxides prepared by rapid thermal nitridation (RTN) has been studied. The radiation was performed by exposing devices to 50 keV x ray to a dose of 0.5 Mrad (Si). Compared to conventional thermal oxides, the rapid thermal nitrided oxide devices exhibit much less increase in the interface state density (Dit). In addition, it is found that higher RTN temperatures and/or longer durations produce smaller ΔDit. The significant reduction of the interface state generation has been attributed to the strain relief effect due to the incorporation of nitrogen at the Si/SixNyOz interface. The bond strain related models have been discussed to explain the results.

Formation Of Shallow Junctions With TiN x O y /TiSi 2 Ohmic Contacts For Self-Aligned Silicide Technology

The formations of TiNx0y/TiSi2 bilayer on Si by rapid thermal nitridation of titanium silicide in NH3 as well as p+/n shallow junction using doped silicide technique have been studied. Results of the chemical stability of TiNx0v/TiSi7/Si in dilute HF, the effectiveness of TiNx0, on TiSi2 as a diffusion barrier Mr Al boron diffusion in Si02/TiSi,2/Si structure, the surface dopant concentration at the TiSi7/Si interface, and the junction quality are presented. It is found that TiNx0y/TiSi2 bilayer has good chemical stability in dilute HF for 60 sec and acts as an effeentive contact barrier between Al and Si substrate up to 500°C, 30 min. Shallow p±n junction with high boron concentration at the TiSO/Si interface has been formed. P-1-/n diodes and p-channel LDD MOSFETs fabricated using this technology show good I-V characteristics with a reverse leakage current on the order of 10-9A/cm.