Electrical noise and RTS fluctuations in advanced CMOS devices

Ferroelectric capacitors having Pt bottom and top electrodes and a ferroelectric film of composition PbZr0.51Ti0.49O3 (PZT) were fabricated and investigated. The PZT films of thicknesses varying from 0.12 to 0.69 μm were prepared by organometallic chemical‐vapor deposition. Annealed capacitors were investigated by capacitance, hysteresis, and pulse switching measurements. It is found that the thickness dependence of the reciprocal capacitance, the coercive voltage, and the polarization measured by pulse switching can all be explained by a blocking layer model, in which a dielectric layer of thickness dbl and relative permittivity ebl is situated between the PZT film and an electrode. It is shown that (i) the coercive field is independent of thickness having a value of 2.4 V/μm; (ii) the ratio ebl/dbl is in the range 20–28 nm−1; (iii) the voltage across the blocking layer is proportional to the polarization, Vbl=cP, where c=4.1±0.5 V m2/C; and (iv) the polarization depends on the electric field in the PZT layer, independent of thickness. Pulse switching endurance measurements showed that in the saturation range the fatigue for these ferroelectric capacitors is determined by the pulse voltage and is independent of the thickness.

Ferroelectric properties and fatigue of PbZr0.51Ti0.49O3 thin films of varying thickness: Blocking layer model

Research on shunted piezoelectric transducers, performed mainly over the past decade, has generated new opportunities for control of vibration and damping in flexible structures. This is made possible by the strong electromechanical coupling associated with modern piezoelectric transducers. In vibration control applications, a piezoelectric transducer is bonded to, or embedded in a base structure. As the structure deforms, the piezoelectric element strains and converts a portion of the structural vibration energy into electrical energy. By shunting the piezoelectric transducer to an electrical impedance, a part of the induced electrical energy can be dissipated. Hence, the impedance acts as a means of extracting mechanical energy from the base structure. This paper reviews recent research related to the use of shunted piezoelectric elements for vibration damping and control. In particular, the paper presents an overview of the literature on piezoelectric shunt damping and discusses recent observations on the feedback nature of piezoelectric shunt damping systems.

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A survey of recent innovations in vibration damping and control using shunted piezoelectric transducers

Research on shunted piezoelectric transducers, per- formed mainly over the past decade, has generated new opportuni- ties for control of vibration and damping in flexible structures. This is made possible by the strong electromechanical coupling associ- ated with modern piezoelectric transducers. In vibration control applications, a piezoelectric transducer is bonded to, or embedded in a base structure. As the structure deforms, the piezoelectric el- ement strains and converts a portion of the structural vibration energy into electrical energy. By shunting the piezoelectric trans- ducer to an electrical impedance, a part of the induced electrical energy can be dissipated. Hence, the impedance acts as a means of extracting mechanical energy from the base structure. This paper reviews recent research related to the use of shunted piezoelec- tric elements for vibration damping and control. In particular, the paper presents an overview of the literature on piezoelectric shunt damping and discusses recent observations on the feedback nature of piezoelectric shunt damping systems.

A Survey of Recent Innovations in Vibration Damping

The stabilities of Pt/Ti bilayer metallizations in an oxidizing atmosphere have been investigated with several thicknesses of interfacial Ti‐bonding layers. Reactions in the Pt/Ti/SiO2/Si interface were examined as a function of various annealing conditions in the temperature range 200–800 °C by using Rutherford backscattering spectrometry, Auger electron spectroscopy, x‐ray diffraction, and transmission electron microscopy. Thermal treatment in oxygen was found to cause rapid oxidation of the Ti layer, accompanied by the migration of Ti into the Pt film. Diffusion of oxygen through the Pt grain boundaries was mainly responsible for the adverse reactions at the interface and loss of mechanical integrity. Thin Ti (10 nm) layers resulted in the depletion of the interfacial bonding layer causing serious adhesion problems, whereas thicker Ti films (100 nm) caused the formation of TiO2−x in the Pt‐grain boundaries, ultimately encapsulating the Pt surface with an insulating TiO2 layer. Improved stability and adhesion in the Pt/Ti bilayer metallization compatible with ferroelectric thin film processing, were achieved by incorporating well reacted thin TiO2 layers in situ, and depositing Pt films at a high temperature.

Investigation of Pt/Ti bilayer metallization on silicon for ferroelectric thin film integration

We report a method for passive piezoelectric shunt-damping of multiple vibration modes using a single piezoelectric transducer (PZT). The method, which is different from other multiple-mode shunting, is to employ a 'blocking' circuit in series with each parallel resistor-inductor shunt circuit designed for one structural mode. The 'blocking' circuit consists of one parallel capacitor-inductor antiresonant circuit or a series of them. The number of antiresonant circuits in each branch circuit depends on the number of the structural modes to be shunt-damped simultaneously. These antiresonant circuits are designed to produce infinite electrical impedance, or antiresonance, at the natural frequencies of all other resistor-inductor shunt circuits. Each branch circuit is functional only at its own mode frequency but is open-circuited at all other mode frequencies. Therefore, when all branches are connected to the PZT terminals, they do not interfere with each other. The method is also easier and more reliable for fine-tuning and optimization operation. We analyze first the multiple-mode shunt-damping circuit with both the generalized circuit and the modified circuit derived from it which is to reduce the number of antiresonant circuits and to make the circuit operation simpler. Experimentally we have employed modified shunt circuits and successfully demonstrated vibration reduction of two and three structural modes using a single PZT transducer bonded on a two-wing aluminum cantilever beam. For three-mode shunt damping, the resonant amplitudes at 206, 348.5, and 484.5 Hz are reduced for 13.28, 7.30, and 9.45 dB, respectively.

Method for multiple-mode shunt damping of structural vibration using a single PZT transducer

The theoretical analysis of an improved piezoelectric shunt using a piezoelectric PZT element shunted with a parallel resistor and inductor circuit for passive structural damping and vibration control was studied. In this paper, we report results of the experiments of the improved shunting technique which were performed and demonstrated successfully for passive vibration control in the ARPA consortium SPICES program on several structures including thermoset fiberglass/epoxy composite plates with embedded PZT patches and cantilever beams with surface bonded patches. Vibration reductions on resonant response of more than 17 dB using the single mode shunting have been obtained on an 18' by 18' by 0.5' composite plate with eight embedded PZT patches. When we excite another composite plate with a commercial compressor mounted on top of it and turn on the shunt circuits, the transmitted vibration level measured with a force gauge at a plate mounting post is reduced about 15 dB. The improved piezoelectric shunting technique has been studied further to shunt-damp multiple vibration modes using only a single PZT patch. The experimental result of the multiple mode shunting also is presented.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Structural vibration damping experiments using improved piezoelectric shunts

We report a method for passive piezoelectric shunt-damping of multiple vibration modes using a single piezoelectric transducer (PZT). The method, which is different from other multiple-mode shuntin...

Method for Multiple Mode Piezoelectric Shunting with Single PZT Transducer for Vibration Control

In a system for in-situ delamination detection in composites, the invention employs a system which evaluates the mechanical vibration response of composite material structures. The damping characteristics of the composite structure are extracted from the detected wave properties generated by imbedded piezoelectric ceramic actuators and received by imbedded high strain sensitive fiber optic sensors. Such a sensor system is simple to operate for real-time non-destructive strain and displacement monitoring and delamination detection, without the need to remove the tested surface from operation. During the routine structural integrity monitoring operation, mechanical vibration pulses are launched into the composite from one actuator. The strain signal's propagation patterns are measured in real time by the fiber-optic sensors at different grating locations. Different travel times are computed dependent on the location of the receiving gratings. Propagation of the waves through a delaminated area results in wave modal properties (damping characteristics) which show a difference from those propagating through the delamination-free area. Successive signals from different locations permit computation of the location of the delamination defect.

System for in-situ delamination detection in composites

Very thin lead‐zirconate‐titanate films, 500 A or less in thickness, have been prepared on Pt‐Ti metallized silicon wafers by a sol‐gel processing technique. Excellent ferroelectric, dielectric, and structural properties have been demonstrated. The maximum polarization and the remanent polarization at a switching voltage of 3 V on a film with a Zr/Ti ratio of about 50/50 are 33 and 12 μC/cm2, respectively. The capability of reaching a saturation polarization at a low voltage (∼3 V) on these films suggests that they are very attractive for use in radiation‐hard low‐voltage nonvolatile programmable random access memories.

S. Y. Wu

Papers

Method for multiple-mode shunt damping of structural vibration using a single PZT transducer

Structural vibration damping experiments using improved piezoelectric shunts

Method for Multiple Mode Piezoelectric Shunting with Single PZT Transducer for Vibration Control

System for in-situ delamination detection in composites

Observations of ferroelectric polarization reversal in sol‐gel processed very thin lead‐zirconate‐titanate films