Chul-Ju Kim

FABRICATION AND CHARACTERIZATION OF MFIS-FET USING Bi3.25La0.75Ti3O12/ZrO2/Si STRUCTURE

ABSTRACT A metal-ferroelectric-insulator-semiconductor structure (MFIS) has been fabricated by ZrO2and Bi3.25La0.75Ti3O12 as the buffer layer and ferroelectric film in forming MFIS diodes on Si(100) substrates, respectively. ZrO2 films were prepared by a sol-gel method. Then, they were carried out dry O2 annealing in a rapid thermal annealing (RTA) furnace at 700°C for 10 min. On the ZrO2/Si structures, Bi3.25La0.75Ti3O12 films were deposited by sol-gel method and they crystallized rapid thermal annealing in O2 atmosphere at 750°C for 30 min. They were characterized by X-ray diffraction analysis (XRD) and atomic force microscopy (AFM). The memory window width in capacitance-voltage(C-V) curve of the Au/BLT/ZrO2/Si diode was about 1.0 V for a voltage sweep of ± 4 V. Base on these results, we fabricated the MFIS-FET structure. The memory window width in drain current–gate voltage (ID–VG) curve of the MFIS-FET was about 0.7 V.

FORMATION OF (Bi,La)4Ti3O12 FILMS ON Si(100) SUBSTRATES USING ZrO2 BUFFER LAYERS

ABSTRACT The ferroelectric behavior of (Bi,La)4Ti3O12 (BLT) films deposited on Si(100) substrates with the use of ZrO2 buffer layers was demonstrated. ZrO2 films were prepared using the sol-gel method. Then, they were subjected to dry O2 annealing in a rapid-thermal-annealing furnace. BLT films were deposited on these structures through the sol-gel method, and they were characterized through X-ray diffraction analysis and atomic-force microscopy. It was found from capacitance-voltage measurements that the BLT films had a hysteresis loop and that the memory window was about 2 V for the voltage sweep of ±5 V. Based on these results, it can be concluded that the use of the BLT/ZrO2/Si(100) structure in the fabrication of MFISFETs (metal-ferroelectric-insulator-semiconductor field-effect transistors) holds great promise.

Effect of Thickness on Electrical Properties of PVDF-TrFE (51/49) Copolymer

In this study, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) in the composition from 51/49, was deposited on platinum for a metal-ferroelectric-metal structure. From XRD patterns, the 70 nm- and 140 nm-thick PVDF-TrFE films showed the intensity peak of near connected to a ferroelectric phase. Moreover, the thicker film indicated the higher intensity than thinner one. The difference of the remanent polarization (2Pr) at 0 V is decreased gradually from 10.19 to as the thickness decrease from 140 to 70 nm. However, when the thickness decreased to 50 nm, the 2Pr rapidly drop to so the minimum critical thickness might be at least 70 nm for device. Both different thickness films, 70 and 140 nm, indicated that the characteristic of current density-voltage was measured for below 15 V and the thicker film maintained relatively lower current density than thinner one. From these results, we can expect that the electrical properties for the devices particularly ferroelectric thin film transistor using PVDF-TrFE copolymer were able to be on the trade-off relationship between the remanent polarization with the bias voltage and the leakage current.

Orientation Control of (Bi,La)4Ti3O12 Thin Films Derived by Sol-Gel Method

BLT ((Bi,La) 4 Ti 3 O 12 ) thin films with (117)- and (00l)-preferred orientation were fabricated on Pt/Ti/SiO 2 /Si(100) substrates by a sol-gel method. Films were annealed in O 2 ambient at 750°C for 30 min to crystallize material. In this crystallization process, the temperature heating rate was changed from 0.5°C/sec to 300°C/sec. It was shown from XRD and XRD reciprocal space mappings analyses that the BLT films with (117)-preferred orientation were formed at lower temperature rate, while the films with c-axis preferred orientation were formed at higher heating rate. The remanent polarization (2 P r ) values of the BLT films with (117)- and (00l)-preferred orientation were 36 and 10 μ C/cm 2 , respectively. SEM showed that the (117)-oriented BLT films are composed of peg-like small grains. On the other hand, large platelet-like grains were found in (00l)-oriented BLT films.

A Novel Quad-band Internal Antenna with Ni/Ag/Ni Structure for Wireless Mobile Handset

An internal antenna handset with the Sputter-deposited Ni/Ag/Ni hetero structure has been extended for the first time to the domain of wireless mobile propagation device. Efficiency distribution image for optimized at 870MHz and 1990MHz, total efficiency result are 47% and 55% in par field condition, respectively. From CST results the simulated current distribution densities are 98.8A/m and 39.8A/m at 870MHz and 1990MHz, respectively. Main objective of this research is characteristics comparison with VSWR and S11 also include radiation pattern performance.

A novel micro-structure internal antenna with sputter-deposited for wireless communication applications

This research proposes a novel micro-structure sputter-deposited internal antenna for wireless communication applications. With the proposed antennas adapted micro and nano scale technology as well as sputter-deposited internal antenna covering GSM quad-band (GSM850/EGSM900 and DCS1800/PCS1900) and WCDMA dual-band (WCDMA850/1900). To present micro-structure Ni/Ag/Ni thin films overall size is 43.0×22.0×0.0015 mm3 (Ni/Ag/Ni growth thickness: 15.0×103 Å) without feeding mechanism. The optimized tri-structure antenna results of shows satisfied performance at GSM quad-band frequency using Agilent E5071B and CTIA chamber. This investigated proposes novel structure is very promising for the quad-band mobile antenna applications and further higher frequency operation of the wireless technology

Internal Antenna Handset with Ni/Ag/Ni Hetero Structure

Abstact---An internal antenna handset with the Sputter-deposited Ni/Ag/Ni hetero structure has been extended for the first time to the domain of wireless mobile propagation device. Efficiency distribution image for optimized at 870MHz and 1990MHz, total efficiency result are 47% and 55% in par field condition, respectively. From CST results the simulated current distribution densities are 98.8A/m and 39.8A/m at 870MHz and 1990MHz, respectively. Main objective of this research is characteristics comparison with VSWR and S11 also include radiation pattern performance.

BLT/STA/Si Structure for MFIS in an NDRO-Type Ferroelectric Random Access Memory

Ferroelectric (Bi,La) 4 Ti 3 O 12 (BLT) thin films were prepared on a p-type Si (100) wafer with a SrTa 2 O 6 (STA) buffer layer for a metal-ferroelectric-insulator-silicon (MFIS) structure. The STA buffer layer was completely crystallized at the high temperature over 800°C. We observed that STA thin films fabricated at 900°C for 3 minutes in O 2 ambient had good insulating properties. Their EOT value was about 5.7 nm. Considering the distribution of the bias voltage on a series capacitor, the ferroelectric BLT and the dielectric STA, BLT thin films with a different thickness were formed on STA/Si structures and characterized by C-V measurement including memory windows. It was found that the memory window width was about 1.5 V for the ±5 V bias sweeping with the 600 nm thick BLT films on STA/Si structure. The leakage current density was about 1.0 × 10−7 A/cm 2 at 5 V. These results are useful and promise the realization of a MFIS structure with the BLT and a STA layer for non-destructive read-out (NDRO) type ferroelectric memories.