Chyuan Haur Kao

Physical and electrical characteristics of the high-k Ta2O5 "tantalum pentoxide… dielectric deposited on the polycrystalline silicon

The high-k Ta2O5 films deposited on the polycrystalline silicon treated with different postrapid thermal annealing temperatures were formed as high-k interdielectrics. Physical and electrical characteristics of the Ta2O5 dielectrics were investigated with x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and electrical analysis. The annealing at 800 °C was found to be the optimal condition to reduce the defects and interface traps existed in the interface between the Ta2O5 dielectric and polysilicon to fabricate a well-crystallized film with higher breakdown field, lower leakage current and smaller charge trapping rate. This Ta2O5 dielectric shows promise for future generation of nonvolatile memory.

Dynamic Negative Bias Temperature Instability (NBTI) of Low-Temperature Polycrystalline Silicon (LTPS) Thin-Film Transistors

The dynamic negative bias temperature instability (NBTI) on low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) was investigated in detail. Experimental results revealed the threshold voltage shift of LTPS TFTs after the NBTI stress decreases with increasing frequency, which is different from the frequency-independence of conventional CMOSFET. Under a low frequency stress, the capacitance-voltage measurement with various frequencies implied that a larger quantity of inversion holes was trapped in the grain boundary. Thus, the difference of the transit time between the grain boundary and interface dominates the LTPS TFTs dynamic NBTI behaviors and results in the dependence of frequency.

Oxide Grown on Polycrystal Silicon by Rapid Thermal Oxidation in N2O

In this paper, rapid thermal processing (RTP) N 2 O polyoxides were studied in terms of oxidation temperature and thickness with O 2 oxidation polyoxides as comparison. Atomic force microscopy, transmission electron microscopy, and secondary ion mass spectroscopy measurements were employed to correlate the electrical characteristics with the physical structures. Results showed that RTP N 2 O-grown polyoxides exhibited better characteristics on the leakage current, E b d , trappings and Q b d . It was found that it was the proper amount of nitrogen incorporated in the polyoxide improving the interface of the polyoxide/polysilicon, consequently improving the electrical quality. The initial hole-trapping phenomenon during the constant current stress, which was due to the incorporated nitrogen, was also observed in the N 2 O-grown polyoxides. The two-step RTP process, i.e., first RTP oxidizing the polysilicon in O 2 and then RTP oxidizing in N 2 O, could achieve polyoxide of good characteristics by incorporating the proper amount of nitrogen into the polyoxide.

The Investigation of the High-k Gd2O3 (Gadolinium Oxide) Interdielectrics Deposited on the Polycrystalline Silicon

The high-k Gd 2 O 3 films deposited on polycrystalline silicon treated with different post rapid thermal annealing (RTA) temperatures were formed as high-k interdielectrics. A combinational electrical and material analysis on the samples was performed to obtain a thorough understanding of annealing effect on the high-k Gd 2 O 3 interdielectrics. The annealing temperature at 900°C was the optimal condition to reduce the defects and interface traps and hence improve material quality to fabricate a well-crystallized film. This high-k Gd 2 O 3 interdielectric shows promise for future generation of nonvolatile memory applications.

Electrical and Reliability Improvement in Polyoxide by Fluorine Implantation

We show that the incorporation of fluorine into the oxide grown on polysilicon (polyoxide) not only improves the electrical characteristics (i.e., lower leakage current, higher electrical breakdown field), but also improves the reliability (lower electron trapping rate, larger Q bd ). This improvement is believed to be due to the stress relaxation of the polyoxide and smoother polysilicon/polyoxide interface by the fluorine incorporation. The optimum fluorine dose (2 X 10 14 ) shows the best characteristics such as E bd over 12 MV/cm and Q bd ∼ 2 C/cm 2 . However, excessive fluorination (1 X 10 15 ) seems to result in performance degradation due to the generation of nonbridging oxygen centers.

Multianalyte biosensor based on pH-sensitive ZnO electrolyte–insulator–semiconductor structures

Multianalyte electrolyte–insulator–semiconductor (EIS) sensors with a ZnO sensing membrane annealed on silicon substrate for use in pH sensing were fabricated. Material analyses were conducted using X-ray diffraction and atomic force microscopy to identify optimal treatment conditions. Sensing performance for various ions of Na+, K+, urea, and glucose was also tested. Results indicate that an EIS sensor with a ZnO membrane annealed at 600 °C exhibited good performance with high sensitivity and a low drift rate compared with all other reported ZnO-based pH sensors. Furthermore, based on well-established pH sensing properties, pH-ion-sensitive field-effect transistor sensors have also been developed for use in detecting urea and glucose ions. ZnO-based EIS sensors show promise for future industrial biosensing applications.

Performance and reliability improvements in thin-film transistors with rapid thermal N2O annealing

In the work, we applied TEOS CVD oxides as gate dielectrics for TFTs with RTN2O annealing combined with NH3 plasma passivation. This process yielded improved electrical characteristics and increased hot-carrier reliability. This is due to the nitrogen pile-up at the poly-Si/SiO2 interface and the strong Si?N bond formation that terminates the dangling bonds in the grains and at the grain boundaries in the channel region. Using the TEOS CVD oxides with rapid thermal annealing in N2O improves the TFT performance and reliability not only by densifying the deposited CVD oxide but also by incorporating the nitrogen into the gate dielectric and polysilicon channel.

Magnesium Oxide (MgO) pH-sensitive Sensing Membrane in Electrolyte-Insulator-Semiconductor Structures with CF 4 Plasma Treatment

Magnesium oxide (MgO) sensing membranes in pH-sensitive electrolyte-insulator-semiconductor structures were fabricated on silicon substrate. To optimize the sensing capability of the membrane, CF4 plasma was incorporated to improve the material quality of MgO films. Multiple material analyses including FESEM, XRD, AFM, and SIMS indicate that plasma treatment might enhance the crystallization and increase the grain size. Therefore, the sensing behaviors in terms of sensitivity, linearity, hysteresis effects, and drift rates might be improved. MgO-based EIS membranes with CF4 plasma treatment show promise for future industrial biosensing applications.

Polarity Asymmetry of Polyoxide Grown on Phosphorus In Situ Doped Polysilicon

-doped polysilicon. It may be not only the surface roughness between the polysilicon/polyoxide interfaces, but also thephosphorus distribution in the interfaces. For the phosphorus in situ doped poly film, the phosphorus piled up at the poly-1/polyoxide interface should result from the out-diffusion of the poly-1 doping during the tetraethyl orthosilicate oxide depositionprocess. However, the phosphorus concentration near the polyoxide/top poly-2 interface was lower than the bulk concentration ofthe polysilicon film, which may result from insufficient phosphorus concentration near the polyoxide/top poly-2 interface withoutsubsequent annealing and dopant activation. Therefore, this may affect the polarity asymmetry of the electrical characteristics forthe phosphorus in situ doped samples. Especially, the thermal polyoxide had the largest polarity asymmetry due to very highphosphorus concentration piled up in the bottom poly-1/polyoxide interface. We also show that the top poly-2 doping processaffects the phosphorus distribution in the polysilicon/polyoxide interfaces, and further, affects the polyoxide performance.© 2006 The Electrochemical Society. DOI: 10.1149/1.2217307 All rights reserved.Manuscript submitted December 27, 2005; revised manuscript received April 3, 2006. Available electronically July 20, 2006.

Influence of NH 3 plasma and Ti doping on pH-sensitive CeO 2 electrolyte-insulator-semiconductor biosensors

In this study, CeO2 pH-sensitive sensing membranes in electrolyte-insulator-semiconductor structures on silicon substrate were fabricated. To enhance sensing performance, the membrane underwent Ti doping and NH3 plasma treatment on the surface. To examine the effects of Ti doping and plasma treatment, multiple material properties evaluations were conducted using field-emission scanning electron microscopy, X-ray diffraction, atomic force microscopy, and secondary ion mass spectroscopy. Results indicate that Ti doping and plasma treatment can remove defects and enhance crystallization, thereby achieving improved pH-sensing performance of the membrane with high sensitivity, high linearity, low hysteresis voltage and low drift voltage. CeO2-based EIS membranes with Ti doping and NH3 plasma treatment show promise for future portable pH-sensitive biosensors.