P. C. Chen

FUNDAMENTAL ELECTRICAL PROPERTIES OF FLUORINATED AND N2O PLASMA-ANNEALED ULTRATHIN SILICON OXIDES GROWN BY MICROWAVE PLASMA AFTERGLOW OXIDATION AT LOW TEMPERATURES

A technique for growing ultrathin silicon oxides of superior quality at low temperatures is indispensable for future submicron device applications. Fundamental characteristics such as the oxide breakdown fields, oxide charges, and interface‐state densities of various ultrathin silicon oxides (≤8 nm) grown by microwave plasma afterglow oxidation at low temperatures (400 and 600 °C) were investigated. Fluorination (HF soaking) and low‐temperature N2O plasma annealing were employed to improve the properties of the oxides. The breakdown fields of the as‐grown silicon oxides were enhanced and the interface‐state densities were reduced. The effect of N2O annealing time on the interface‐state density was also investigated. A longer annealing time (≳1 h) was required to reduce the interface‐state density. The effective oxide charge density of 600 °C as‐grown oxide was as low as 6×1010 cm−2. Additionally, the breakdown field of the thin silicon oxide grown at 600 °C with 15 min N2O plasma annealing was 12 MV/cm.

Study on the photoconductivity characteristics of porous Si

After the report of the visible light emission out of porous Si,’ this material regained a lot of attention in the hope that optoelectronics in group IV materials can someday be mature. However, many essential subjects about it, such as the formation mechanism, the structure, and the origin of visible light emission, remain controversial. While most work has focused on the optical properties of porous Si, not much effort was paid to the electrical aspects. Bilenko et al. ’ measured the electrical conductivity and the Hall coefficient of porous Si. Beale et aZ. 3 used two and four terminal measurements to obtain the resistivity of porous Si. Both works did not present current-voltage (I-V) characteristics. Some recent workG reported the I-V curves of metal-porous Si junctions. In these works, the current flowed through the junction and the porous layer along the direction of electrochemical etching. Results showed that metal-p-type porous Si junctions have Schottky junctionlike behavior while metal-n-type porous Si junctions tend to be ohmic. Despite these, detailed study on the I-V characteristics and the transport mechanism of carriers in porous Si is lacking. As a matter of fact, better understanding in the electrical transport properties of porous Si is not only important to electroluminescence and other photosensitive devices design but also helpful to understanding the structure of porous Si itself. In this work, we present a study on the electrical transport property of porous Si. Detailed I-V characteristics for currents flowing perpendicular to the etching direction are shown. Obvious oscillations in the I-V curves due to photoconductivity have been observed. p-type layers were formed on n-type Si wafers with resistivities of 4-7 L! cm by using low energy boron implantation (dose= 10’5/cm2, energy=25 keV, 50 keV), and thermal annealing at 950 “C for 20 min. The junction depths were determined by the spreading resistance method as 0.52-0.61 pm, and the average value of the resulting doping level was about 1019/cm3. Gold with 500 pm separations were evaporated on the surface. Porous Si was formed by electrochemical anodization without illumination in HF solutions in the region between contacts. Porosity was difficult to be determined accurately in our case. The concentration of HF solution was 10%. The etching

Ultra-thin gate dielectrics grown by low-temperature processes for applications to ULSI devices

Abstract When the dimension miniaturization of ultra-large-scale integrated (ULSI) devices is reduced below 0.25 μm, ultra-thin gate dielectrics (

Improvement on properties and reliability of ultra-thin silicon oxide (3-5 nm) grown by microwave plasma afterglow at the low temperatures using mixtures of N2O and O2

Abstract Ultra-thin silicon oxides (4 nm) with excellent quality were grown by using mixture of N 2 O and O 2 plasma in a microwave afterglow plasma oxidation system. The electrical breakdown fields of oxide grown with a mixture of N 2 O and O 2 plasma are comparable with that of conventional thermally grown oxides. The interface state densities are lower and charge to breakdown are higher than that of oxide grown in traditional thermal furnace. The optimal interface state density (∼3×10 10 cm −2 eV −1 ) could be achieved by tuning the N 2 O/O 2 ratio. The oxides grown with a lower microwave power and a lower gas flow rate possess lower interface state density. Higher value of charge to breakdown could be found in oxides grown at low gas flow rate. Resistance to tunneling current stress increased as the ratio of N 2 O/O 2 in plasma is higher. All these improvements could be attributed to the incorporation of nitrogen into oxides grown at lower temperatures in our novel system.

Study on the Fundamental Electrical Properties of Ultra-Thin Oxides Grown by Low Temperature Microwave Plasma Afterglow Oxidation

Fundamental characteristicssuch as the oxide breakdown fields, oxide charges and interface state density of various ultra-thin oxides (< I nm) grown by microwave plasma afterglow oxidation at l-ow temperatures were investigated. The ef fective oxide charge density of 600 oC as-grown oxide was as low as 6x1010 cm-Z. The breakdown fields of the oxides were further enhanced and the interface state densities were reduced by employing fluorination (Hr soaked) and low temperature luZO pflsmi annealing. A-5-2

Improvements on Electrical Properties of Ultra-Thin Silicon Oxides Grown by Microwave Afterglow Oxygen Plasma

Fundamental characteristics such as the oxide breakdown fields, oxide charges and interface state density of various ultra-thin silicon oxides (≤ 8 nm) grown by microwave plasma afterglow oxidation at low temperatures (400 °C and 600 °C) were investigated. The effective Oxide charge density of 600 °C as-grown oxide was as low as 6×10 10 cm -2 . The breakdown fields of the oxides were further enhanced and the interface state densities were reduced by employing fluorination (HF soaked) and low temperature N 2 O plasma annealing. The breakdown field of the thin oxide grown at 600 °C with 15 min N 2 O plasma annealing was 12 MV/cm. The reduction of interface state density was about 35% for 600 °C fluorinated oxide. When integrated with poly-gate process, the interface state density was as low as 5×10 10 cm -2 eV -1 .

A study on the current-voltage characteristics of porous silicon

Abstract We utilized the conventional planar fabrication techniques and the electro-chemical etching method to prepare porous Si layers in the p-type region of a p-n junction, which makes the study on the transverse transport property of this material possible. The junctions were fabricated by shallow diffusion or low energy ion-implantation, with porous Si formed perpendicular to the junction and between two ohmic contacts. This structure confines currents to the direction parallel to the surface. Various junction depths and etching depths were tried. The porous Si structure was examined by XTEM and correlated with the electrical data. A distinct photoconductivity feature has been observed.