Non-nitrided Oxide Research Articles

A Study of NBTI and Short-Term Threshold Hysteresis of Thin Nitrided and Thick Non-Nitrided Oxides

Negative bias temperature instability (NBTI) degradation and recovery have been investigated for 7-50-nm non-nitrided oxides and compared to thin 1.8- and 2.2-nm nitrided oxides from a dual work function technology. A wide regime of stress fields from 2.5 to 10 MV/cm has been covered. Thermal activation has been studied for temperatures from 25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> C to 200 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> C. The NBTI effect for the nitrided oxide is larger than for non-nitrided oxides. The percentage of threshold shift <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> which is ldquolostrdquo during a long measurement delay-which is the quantity leading to curved <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> versus stress-time curves and to errors in extrapolated lifetimes-is about equal for nitrided or thick non-nitrided oxides. The fraction of recovered <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is strongly dependent on stress time but only weakly dependent on stress field. Recovery in thick oxides leads to exactly the same problems as for non-nitrided oxides, and clearly, a fast measurement method is needed. The effect of short-term threshold shifts has been studied for extremely short stress times down to 200 ns.

Characteristics of Post-Nitridation Rapid-Thermal Annealed Gate Oxide Grown on 4H-SiC

In this paper, the electrical properties of pre- and post-rapid thermal annealed 4H SiC-based gate oxide grown in 10% nitrous oxide (N2O) and in dry oxygen have been investigated, compared, and reported for the first time. After treating the nitrided gate oxide in rapid thermal annealing (RTA), oxide breakdown characteristic has been improved significantly. This improvement has been attributed to the reduction of SiC–SiO2 interface-trap density and the generation of positive oxide charge, acting as an electron-trapping center. However, deleterious effects have been observed in non-nitrided oxide after subjected to the same RTA treatment. The differences in oxide-breakdown strength of these oxides have been explained and modeled.

Charge relaxation in nitrided and non-nitrided sputtered oxide

The charge relaxation of nitrided silicon oxide was studied in an MOS structure. Oxynitrides were formed by reactive sputtering in an Ar/O 2/N 2 plasma from a silicon oxide target. The nitrogen mixing ratio was varied from 0% to 20%, with the argon mixing ratio kept at 80%. The electrical stress was performed with injection from an aluminium gate and the relaxation of stress-induced charge under floating and gate bias conditions was monitored via mid-gap voltage and interface states density measurement in a time interval from 1 min to about four months. A trend that nitrided oxides experience more relaxation of mid-gap voltage was observed while non-nitrided oxide had the largest relaxation of interface states density in the same time interval. We suggest that relaxation under applied bias due to the stress-induced charge is, in part, due to the slow states.

Ultrathin Gate Oxides with Shallow Nitrogen Implants as Effective Barriers to Boron Diffusion

ABSTRACTPlasma immersion ion implantation (PIII) has been employed to controllably place nitrogen ions from an inductively coupled plasma into a thin furnace grown gate oxide 2.0nm thick with implant voltages from 25 to 500V. Control of the implant energy enables shallow implantation confining the nitrogen mainly within the oxide. Rapid thermal annealing is essential in repairing any damage to the implanted silicon dioxide and silicon while consolidating the bonding of nitrogen into the oxide film prior to gate polysilicon deposition. High frequency capacitance-voltage measurements of capacitors made with BF2+ implanted gates throughout a series of furnace anneals demonstrates the efficiency for blocking boron compared to non-nitrided oxides of similar thickness. Tddb measurements verify excellent reliability compared to a non-implanted oxide for both stress polarities.

Charge Trapping Properties of Thin Plasma Nitrided Oxides Induced by Nitrogen and Hydrogen Incorporation

ABSTRACTIn this work, we report the effects of an ammonia plasma nitridation on the charge trapping properties of thin SiO2 films in correlation with their nitrogen and hydrogen contents. Electron traps characteristics were determined by die avalanche injection technique. Hydrogen contents were measured by Elastic Recoil Detection analysis (ERDA). Nitrogen depth profiles were obtained with Auger spectroscopy. It is shown that the bulk electron trapping properties are essentially controlled by the specificity of hydrogen and nitrogen incorporation in the SiO2 films during the ammonia plasma process. For short nitridation times, an increase of hydrogen related electron trap densities is observed in good agreement with hydrogen ERDA measurements. However hydrogen concentration never exceeds 3 at% and can be scaled down by a short time post-nitridation anneal in oxygen, to a level comparable indeed inferior to that of a non-nitrided oxide. For heavy nitridation, an additional electron trap is detected which could be associated to the presence of nitrogen in the bulk of SiO2.

Boron diffusion effects from p+ polysilicon gate in thin thermal oxide and plasma nitrided oxide

The effects of boron diffusion into thermal and plasma nitrided thin oxide are studied on p+ poly gate capacitors. For N 2 anneal at 950°C longer than 30 mn, interface state generation, enhanced electron trapping rate and reduction in Qbd are found for the non-nitrided oxide. Light plasma nitridation suppresses these detrimental effects while preserving the integrity of the Si/SiO 2 interface.