Atsushi Noma

GaAs MMIC Chip-sets for mobile communication systems with on-chip ferroelectric capacitors

Abstract GaAs microwave monolithic integrated circuits (MMICs) with Ba1−XSrXTiO3 (BST) capacitors have been developed. Spin-coating of sol-gel solution was used to make the BST thin film. The obtained BST film has a dielectric constant of 300 that is 50 times higher than the conventional SiN one. The capacitance has the frequency roll-off over 2 GHz, which is sufficient enough for a variety of consumer applications. The implemented GaAs MMICs with on-chip BST capacitors enable the positive-bias supply and high gain performance as well as the small package outline.

Reliability study on bst capacitors for gaas mmic

Abstract Reliability of BST (Ba0.7Sr0.3TiO3) capacitors made by using a MOD technique was studied in terms of TDDB. DLTS analysis revealed peakshift toward the lower-temperature side as the degradation goes further. Obtained energy level of interfacial states at grain boundaries was 0.75eV. We found the capture cross section of the level increases after the bias-temperature stress. We also found that the larger grain size of BST film gives longer lifetime. These results suggest that the reliability is to be determined by the interface of grains.

Embedded ferroelectric memory technology with completely encapsulated hydrogen barrier structure

A 0.18-/spl mu/m system LSI embedded ferroelectric memory (FeRAM) operating at a very low voltage has been developed for the first time. The low-voltage operation has been attained by newly developed stacked ferroelectric capacitors completely encapsulated by hydrogen barriers, which enable us to eliminate hydrogen reduction of the ferroelectric thin film during the back end of the line process including FSG, tungsten CVD (W-CVD), and plasma CVD SiN (p-SiN) passivation. A fabricated 1-Mbit one-transistor one-capacitor SrBi/sub 2/(Ta/sub x/Nb/sub 1-x/)/sub 2/O/sub 9/ (SBTN)-based embedded FeRAM operates at a low voltage of 1.1 V and ensures the endurance cycles up to 10/sup 12/ at 85/spl deg/C and the data retention time up to 1000 h at 125/spl deg/C, which is the most promising for mass production of 0.18-/spl mu/m low-power system LSI-embedded FeRAM and beyond.

Advanced LSI embedded with FeRAM for contactless IC cards and its manufacturing technology

Abstract High performance LSIs embedded with ferroelectric random access memory (FeRAM) for contactless IC cards are now commercially available. The emphasis is placed on the materials solution with SrBi2(Ta,Nb)2O9 (SBTN) which enables to exploit the potential performance of FeRAMs for composite logic/microcontroller LSIs operating at high speeds and low powers. The leading-edge 0.6-μm and double-level-metal FeRAM technology produces microcontroller-embedded LSIs with 14-kbit or 64-kbit FeRAM. A mature 0.8-μm and single-level-metal process has been built to maximize the die yield. Yields exceeding 90% indicate the excellent process stability. Product qualification data have proven the robust FeRAM technologies.

Thermal Aging Effect in Poled Ferroelectric SrBi2(Ta,Nb)2O9 Capacitors

Changes in the electrical properties of poled ferroelectric SrBi2(Ta,Nb)2O9 (SBTN) thin-film capacitors caused by high-temperature storage were studied. Current–voltage (J–V) characteristics of SBTN capacitors before and after high-temperature storage indicated that the current in SBTN is predominantly carried by electrons and limited by electrode interfaces. The voltage shift in the polarization–voltage (P–V) curve caused at high temperatures was ascribed to a bulk effect because there were no definite changes in the interface-limited J–V characteristics before and after high-temperature storage. Assuming the pinning of domains by capturing electrons emitted from traps distributed in the energy gap, we describe the decay in switchable polarization with the power of time. The activation energy for the decay in switchable polarization associated with electron capture was determined to be 0.23 eV based on the temperature dependence of the decay in switchable polarization.