Publications by Jacek Baborowski

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This paper describes fabrication and characterization results of piezoelectric micromachined ultrasonic transducers (pMUTs) based on 2-mu m-thick Pb(Zr0.53Ti0.47O3) (PZT) thin films. The applied structures are circular plates held at four bridges, thus par ...

A solid oxide fuel cell structure obtainable by selective electrochemical processing, comprising an electrolyte membrane (4) formed by a thin film more than 50nm but less than l0[mu]m thick, covering a supporting structure (1) made of a bulk substrate, the ...

Novel, highly sensitive piezoelectric acoustic sensors based on partially unclamped Pb(Zr-x, Ti1-x)O-3 (PZT) coated cantilever and bridge have been fabricated by silicon micromachining. High sensitivity at low frequencies (5-100 Hz) has been achieved by patterning very narrow slits (3 to 5 mum) around the structures. A typical response of 100 mV Pa-1 and a noise equivalent pressure of 1.6 mPa Hz(1/2) at 20 Hz have been measured using a 10 pF charge amplifier. Stress compensation, dry etching and integration

Ferroelectric capacitive devices for memory and MEMS applications require patterned ferroelectric thin films with high anisotropic etched features. In this paper, physical and chemical parameters during etching of Pb(Zr0.53Ti0.47)O-3 (PZT) by a dual frequency ECR/RF reactor have been investigated. The removal characteristics of blanket films and films with a patterned mask were investigated as a function of gas chemistry (Ar, halogen gases), substrate bias RF power and working pressure (from 5 x 10(-4) Pa t

Ferroelectric thin films for memory and MEMS applications require noble metal or refractory metal oxide electrodes. In this paper, physical and chemical mechanisms during platinum etching by a dual frequency ECR/RF reactor have been investigated. An ion beam was generated by means of a 50 mm diameter ECR-gun directed towards the substrate. The latter was placed on a RF powered electrode for discharging and local activation of reactive gas species. The removal characteristics of blanket platinum films and pl

Ferroelectric thin films for memory and MEMS applications require noble metal or refractory metal oxide electrodes. In this paper, physical and chemical parameters during etching of RuO2 and Pr by a dual frequency ECR/RF reactor have been investigated. The removal characteristics of blanket films and films with a patterned mask (photoresist or SiO2 masks) were investigated as a function of gas chemistry (Ar, O-2, halogen gases), ion beam energy (ion extraction/acceleration voltages), substrate bias RF power

Processing issues for the fabrication of capacitive micromachined ultrasonic transducer (cMUT) arrays have been studied using surface micromachining. This work focuses on the critical steps of process fabrication such as membrane formation, sacrificial layer properties and vacuum sealing performance of cavity. We describe a four-mask process for the realization of sealed cMUT. We demonstrate that the use of a sacrificial layer with a columnar structure gives a fast etching rate (29 nm s(-1)) in a buffered h

Fabrication of high-density ferroelectric memories requires the growth of the ferroelectric material on the drain contact metal. In standard 0.5 mum technology, tungsten plugs are applied to connect the drain contacts to the first metallization level. In this work, we investigated electrode systems to be applied between sputter deposited, ferroelectric PbZr0.35Ti0.65O3 (PZT) and tungsten. Besides the obvious barrier function of such an electrode system, the texture of the PZT is of interest as well. The rou

PZT (PbZrx Ti1-xO3) thin films have been locally grown by means of sol-gel deposition and local annealing on microhotplates. The microhotplates were based on a stress compensated Si3N4 /SiO2 membranes as structural elements and contained tantalum silicide filaments (Ta5Si3) for resistive heating. Above the filaments, a passivation layer of SiO2, an adhesion layer of Ti/TiO2 and a bottom electrode of Pt were deposited. Due to the low heat conductivity of the membrane, crystallization of the PZT film occurs e

In this communication we address two issues essential for low-voltage memory applications of ferroelectric thin films: the size effect on polarization switching, and polarization fatigue. According to the proposed concept, both of these phenomena are controlled by local injection of charge into the interfacial layers of the ferroelectric film. In the experimental part of this work, we show that the entrapped charge relaxation can be enhanced by introducing a thin RuO2 layer into the top interface of the Pt/

Piezoelectric micromachined ultrasonic transducers for airborne and immersed applications working in the frequency range from 20 kHz in liquid to 750 kHz in air have been fabricated and characterized, as well as simulated by finite element modelling. The basic element consisted of a oxidized and platinized silicon membrane coated with a 2 mum thick (100)-textured Pb(Zr,Ti)O-3 (PZT) thin film deposited by sol-gel techniques. SOI wafers have been applied to obtain a good definition of the silicon part of the

There is a need for chemically resistant coatings that protect the exposed surface of microfluidics components. Pinhole free films with low stress and a good uniformity on flat and inclined surfaces are required. In this study, amorphous silicon carbide (SiC) thin films have been deposited by RF magnetron sputtering on hat surfaces and into micromachined cavities of Si (100). The variation of RF power, deposition pressure and substrate bias voltage have been studied. Depending on the deposition conditions,

In this paper the simple accelerometers based on PZT thin films were developed and characterized. The functions of seismic mass and spring are given by a boss loaded cantilever structure. The strain of the cantilever is detected by a Pb(Zr,Ti)O-3 thin film. A 2 mm long and 0.8 mm wide cantilever yielded a response of 0.6 mV/g In the frequency interval between I and 600 Hz. With Delta f = 600Hz a limit of about 1mg* at 1Hz, and less above this frequency, was observed. The response predicted by the analytical

Capacitors in metal-insulator-metal structure have been fabricated with different bottom electrodes. It has been found that the observed losses are enormous at gigahertz frequencies unless due care is taken not only for the conductivity of the bottom electrode but also its thickness. Very thin bottom electrodes (thickness similar to 100 nm) modify the dielectric response substantially and major loss contributions arise from the substrate, the electrode resistance, and the contacts. A simple approach is sugg

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging is employed to characterize the surface of patterned noble metal (Pt) and titania (TiO2) thin films deposited on oxidized silicon wafers. ToF-SIMS is used to follow the different process steps during the thin films patterning as well as the post-processing cleaning. Both positive and negative ToF-SIMS modes reveal the presence of contaminants, due to the etching processes (Cl- Al-,(+)), but only on the etched surfaces. Elements due to the pos

An epitaxial 200 nm thick film of Pb(Zr0.40Ti0.60)O-3 (PZT) has been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3 (100) (STO). The patterning process involved electron-beam lithography of polymethylmethacrylate, fabrication of a 75 nm thick Cr hard mask layer by means of a lift-off process, and dry etching of PZT. The smallest PZT features obtained were 100 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the contact mode revealed a strong increas

Pb(Zr-x, Ti1-x)O-3 (PZT) piezoelectric thin films are of major interest in MEMS technology for their ability to provide electro-mechanical coupling. In this work, the effective transverse piezoelectric coefficient e(31,f) of sol-gel processed films was investigated as a function of composition, film texture and film thickness. Dense, textured and crack-free PZT films have been obtained on silicon substrates up to a thickness of 4 mum. Crystallization anneals have been performed for every 0.25 mum. Nucleatio

New micromachined pressure sensors based on PZT coated silicon cantilevers have been fabricated and integrated in a photoacoustic gas detector. PZT Sol-gel thin films texture and composition were optimized with respect to the transverse piezoelectric coefficient e(31,f). A best value of -12 C/m(2) was obtained with (100)/(001) textured thin films at the MPB composition. Optimum stress compensation between the different layers composing the cantilever has been studied in order to yield flat cantilevers. A hi

A micro-hotplate device, useful in catalytic high-temperature chemical sensors, micro-chemical reactors and as infra-red source, in particular at temperatures above 600 DEG C, comprises a thin film resistive heater (1) made of a refractory metal silicide selected from silicides of tantalum, zirconium, tungsten, molybdenum, niobium and hafnium, the silicide having a polycrystalline structure obtainalble at temperatures above 600 DEG C. The thin film resistive heater (1) is encapsulated between insulating lay

Epitaxial 50 nm and 200 nm thick films of Pb(Zr0.40Ti0.60)O-3 (PZT) have been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3(100) (STO). The patterning process involved electron beam lithography of polymethylmethacrylate (PMMA), fabrication of a 75 nm thick Cr hard mask layer by means of a lift off process, and dry etching of PZT. The smallest PZT features obtained by means of this process were 50 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the

Jacek Baborowski

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Piezoelectric micromachined ultrasonic transducers based on PZT thin films

Metallic supporting grid for ultrathin electrolyte membranes in solid oxide fuel cells

Piezoelectric Pb(Zr-x,Ti1-x)O-3 thin film cantilever and bridge acoustic sensors for miniaturized photoacoustic gas detectors

Mechanisms of Pb(Zr0.53Ti0.47)O-3 thin film etching with ECR/RF reactor

Etching of platinum thin films with dual frequency ECR/RF reactor

Etching of RuO2 and Pt thin films with ECR/RF reactor

Optimization of the fabrication of sealed capacitive transducers using surface micromachining

Tungsten based electrodes for stacked capacitor ferroelectric memories

Local growth of sol-gel films by means of microhotplates

Downscaling of Pb(Zr,Ti)O-3 film thickness for low-voltage ferroelectric capacitors: Effect of charge relaxation at the interfaces

Simulation and characterization of piezoelectric micromachined ultrasonic transducers (PMUT's) based on PZT/SOI membranes

Sputtered silicon carbide thin films as protective coating for MEMS applications

Fabrication and characterization of micromachined accelerometers based on PZT thin films

The effect of bottom electrode on the performance of thin film based capacitors in the gigahertz region

Imaging by time-of-flight secondary ion mass spectrometry of plasma patterned metal and oxide thin films

Size effect in mesoscopic epitaxial ferroelectric structures: Increase of piezoelectric response with decreasing feature size

{100}-textured, piezoelectric Pb(Zr-x Ti1-x)O-3 thin films for MEMS: integration, deposition and properties

Piezoelectric cantilever microphone for photoacoustic GAS detector

High temperature micro-hotplate

Size-effect in mesoscopic epitaxial ferroelectric structures: Increase of piezoelectric response with decreasing feature-size