Joseph D. Cuchiaro

Process optimization and characterization of device worthy sol-gel based PZT for ferroelectric memories

The purpose of this work is to develop and characterize an optimized sol-gel PZT process to be used in ferroelectric memories. A review of the sol-gel process is given, including discussions on hydrolysis under acidic and basic conditions. Application of the sol-gel process to thin films is then discussed. Topics such as removal of solvents, stresses in the thin film and how this relates to cracking are mentioned. A review of different synthesis methods of sol-gel PZT is then conducted in order to help determine a device worthy sol-gel PZT process. Methods of controlling the pore size by hydrolysis and different heat treatments at various stages during the drying and annealing cycles are then used. The quality of thin film PZT on Pt is characterized by using dispersive X-ray and X-ray diffraction analyses. Electrical results yield Pr ranging from 7.9-21.9 μC/cm2Ec ranging from 29.1 -92.3 kV/cm and switching times as fast as 56 ns, using a capacitor area of 1 × 104 μm2. However, these results depend on the...

Characterization of self-patterned SrBi2Ta2O9 thin films from photo-sensitive solutions

Abstract Self-patterned SrBi2Ta2O9 thin films were successfully fabricated from photo-sensitive solutions by means of UV irradiation through photo masks. After conventional baking and wet etching the films were annealed. The photo-sensitive SrBi2Ta2O9 solutions give high resolution negative-pattern of the mask image down to 1 μm line width by deep UV irradiation at 900 mJ/cm2. The capacitor characteristics of the 210 nm thick films fabricated on the Pt/Ti/SiO2/Si substrates by this process showed 2Pr values of 17 μC/cm2, 2Ec of 89 kV/cm, and leakage current densities of 5×10−9 A/cm2 at 5 V. The films showed no fatigue after 1×1011 switching cycles.

Compositional Dependence of Electrical Characteristics in SrBi2Ta2-xNbxO9 Ferroelectric Capacitor Reduced by H2 Annealing

Degradation of electrical properties by annealing in hydrogen ambient is one of the most significant problems associated with ferroelectric oxides used in mainstream nonvolatile memory. A decrease in the degradation of the remanent polarization and the breakdown voltage of a ferroelectric SrBi2Ta2-xNbxO9 (SBTN) capacitor has been attempted by controlling the Ta/Nb ratio, adding excess Bi oxide and adding excess Nb oxide. Substituting Nb for Ta improves the remanent polarization, however, it also leads to a decrease in the breakdown voltage. Excess Bi and Nb oxide both decrease the remanent polarization. Regarding the breakdown voltage, the addition of excess Bi and Nb oxide decrease the amount of the degradation caused by short-time H2-annealing, although it is not enough to prevent the degradation caused by long-time H2 annealing. Furthermore, the reduction path in the ferroelectric capacitor by low-temperature H2 annealing is discussed.

Chemical solution deposition (CSD) and characterization of ferroelectric and dielectric thin films

Abstract This invited paper discusses chemical solution deposition (CSD) and characterization of ferroelectric and dielectric thin films. Liquid Source Misted Chemical Deposition (LSMCD) technology was employed to deposit thin films using Metal Organic Decomposition (MOD) precursors. The configuration of the LSMCD machine along with deposition conditions and parameters are discussed in detail. Thickness uniformity, repeatability and step coverage data are also reported. Finally, electrical properties of thin Y1 and BST films deposited by LSMCD are discussed.

Reduction of the hydrogen degradation in SrBi2(Ta1−xNbx)2O9 by TiN barrier metal

The use of ferroelectric SrBi2(Ta1−xNbx)2O9 (SBTN) as a mainstream form of nonvolatile memory requires that the degradation of its electrical qualities that is caused by annealing in a hydrogen atmosphere be reduced. Titanium nitride (TiN) is a candidate for use as a barrier-metal layer against hydrogen diffusion. The relationship between the degradation in the qualities of SBTN and the quality of the TiN barrier metal has been investigated. TiN when sputtered onto SBTN capacitors creates a good barrier under all sputtering conditions, and maintains the electrical characteristics of the SBTN through annealing in an atmosphere of H2. Higher density TiN films provide more effective protection. The characteristics of the degraded capacitor were investigated in terms of its current-voltage characteristic. Remanent polarization can be recovered from, at least partially, by applying a series of bipolar pulses. This rejuvenation of the electrical qualities indicates that degradation arises from a combination of ...

Preparation of Self-Patterned SrBi 2 Ta 2 O 9 Thin Films from Photo-Sensitive Solutions

Photo-sensitive SrBi 2 Ta 2 O 9 (SBT) solutions were evaluated and the patterning process flow for SBT films using the solutions was optimized. By adding a soft-bake process before UVirradiation, self-patterned SBT films were successfully prepared from the solutions and the cross sectional shape of the patterned films was improved. The photo-sensitivity of the solutions was estimated to be 900 mJ/cm 2 . The photo-reaction in the precursor gel film formed from the solution was traced by measuring IR absorption spectra. The obtained films had excellent ferroelectric properties comparable to conventional SBT films.

Microcontrollers with ferroelectric embedded memory

Summary form only given. This paper describes ferroelectric memories (FRAMs) embedded in microcontrollers. The first device to be commercialized by Panasonic/Symetrix is an 8-bit RISC processor with 64 kbits of FRAM, using the layered Perovskite Y-1 material. This FRAM is implemented using double level metal. An RF-coupled smart card uses this device on a single chip realization of a transponder, power circuit, microcontroller and memory. Further developments are also discussed for higher density devices and controllers of up to 32-bit words.