Ing-Shin Chen

Metalorganic chemical vapor deposition Pb(Zr,Ti)O3 and selected lower electrode structures as a pathway to integrated piezoelectric microelectromechanical systems

The actuation mechanism is an important aspect of many micromachined devices. Electrostatic actuation has been the prevailing actuation method due to its relative ease in implementation using conventional silicon microfabrication techniques. Other mechanisms are becoming more accessible to micromachine designs as new materials are introduced into the microfabrication process. Recent progress in nonvolatile memory has led to successful incorporation of Pb(Zr,Ti)O3 (PZT) thin films into microelectronic devices. The present work expands on this area and investigates PZT thin films and electrode/barrier combinations for applications in micromachined devices. Incorporation of PZT thin films into silicon micromachined devices requires electrode systems and deposition techniques that are compatible with silicon microfabrication. In this study, Ir/IrOx and Ir/(Ti,Al)N lower electrode systems were developed to suppress diffusion of reactive species (e.g., Pb) into silicon-based microelectromechanical system device...

Liquid delivery MOCVD of PLT for pyroelectric detectors

Pb/sub 1-x/La/sub x/Ti/sub 1-x/4/O/sub 3/ (PLT) films have shown promise for uncooled infrared detector applications. A metalorganic chemical vapor deposition (MOCVD) process has been developed to deposit PLT at 535/spl deg/C using the liquid delivery technique on two inch Pt/ZrO/sub 2//Si substrates. Metalorganic /spl beta/-diketonate and mixed /spl beta/-diketonate-alkoxide precursors were flash vaporized and delivered into a large area MOCVD chamber and high quality crystalline perovskite films were deposited with La contents of 0.02/spl les//spl times//spl les/0.28. Room temperature dielectric constant varied between 400 940 for films /spl sim/1200 /spl Aring/ thick and increased with increasing La content. Pyroelectric measurements were carried out using the Byer-Roundy technique. The pyroelectric coefficients were found to depend on film orientation which varied between [100] and [111] with the Pb/Ti ratio; values between 6-13 nC/cm/sup 2/K were observed.

Metalorganic Chemical Vapor Deposition of Thin Film ZrO2 and Pb(Zr,Ti)O3: Precursor Chemistry and Process Characteristics.

Metalorganic chemical vapor deposition (MOCVD) process characteristics of several zirconium source reagents were investigated. These source reagents included metal β-diketonates [e.g., Zr(thd)4 where thd=(2,2,6,6-tetramethyl-3,5-heptanedionate)] and metal alkoxide/β-diketonates [e.g., Zr(OiPr)2(thd)2 and Zr(OtBu)2(thd)2]. Thermal properties and transport behaviors of these precursors were examined by thermogravimetric analysis. Zirconium oxide films were deposited on silicon substrates at reduced pressure. Under the process conditions examined, the deposition behavior was mass-transport controlled, and Zr(OiPr)2(thd)2 and Zr(OtBu)2(thd)2 behaved similarly. The films exhibited low carbon content. Pb(Zr, Ti)O3 (PZT) films were deposited on iridium-coated silicon substrates under reduced pressure. Zirconium incorporation efficiency was significantly improved for Zr(OiPr)2(thd)2 when compared to Zr(thd)4. Use of M(OtBu)2(thd)2 (where M=Zr or Ti) as source reagents for MOCVD of PZT was examined and compared to M(OiPr)2(thd)2 analogues. In this case, higher process pressures were needed to improve the incorporation efficiencies of M(OtBu)2(thd)2 precursors.

Dielectric and pyroelectric properties of thin film PZT

Monolithic integration of thin film uncooled IR detectors requires processes compatible with Si devices and thermal isolation strategies. A metalorganic chemical vapor deposition (MOCVD) process has been developed to address these needs that uses /spl beta/-diketonate and mixed /spl beta/-diketonate-alkoxide precursors in a liquid delivery approach. Process space has been explored, and high quality tetragonal thin Pb(Zr,Ti)O/sub 3/ (PZT) films with nominal Zr/Ti ratios of 20/80 were deposited on Si wafers with Pt electrodes at temperatures between 475 and 550/spl deg/C. Following a post deposition anneal at 650/spl deg/C, permittivities (/spl epsiv/) ranging from 450 to 635 have been observed, along with pyroelectric coefficients (p) from 10 to 25 nC/cm/sup 2/K. Dielectric loss (tan /spl delta/) was approximately 0.015 to 0.025. These values translate to good voltage and signal-to-noise figures of merit (p/c/spl epsiv/ and p/c(/spl epsiv/ tan /spl delta/)/sup 1/2/, respectively) for thin film devices, where c=heat capacity per unit volume. Low thermal budget processing at T/spl les/500/spl deg/C also produced a similar combination of properties which suggest that this process can be used as a back-end fabrication step after the read-out integrated circuits (ROICs) are fully functioning on a Si wafer.

Preparation of Piezoelectric PZT Thin Films by Mocvd for MEMS Applications

Integration of piezoelectric Pb(Zr,Ti)O 3 (PZT) thin films promises to provide silicon-based microelectromechanical systems (MEMS) with added functionality. PZT films with compositions near the tetragonal/rhombohedral morphotropic boundary have been deposited on iridium-coated Si substrates by a thermal chemical vapor deposition (CVD) process using flash vaporized metalorganic precursors. Process variables including (A-site)-to-(B-site) ratios in the precursor mix and deposition times have been surveyed. Stoichiometric, perovskite films with nominal Zr/Ti ratios ranging from 40/60 to 60/40 were obtained. Parallel-plate capacitor structures have been fabricated by depositing Pt top electrodes using e-beam evaporation through shadow masks. Ferroelectric hysteresis loops were measured using a standard ferroelectric tester. Remenant polarization values in the range of 20∼30 μC/cm 2 were obtained. For films of 0.5 μm or thicker, piezoelectric hysteresis loops were characterized by dual-beam interferometry. Longitudinal piezoelectric coefficients (d 33 ) of 30∼60 pm/V were observed on the films deposited between 550 and 600°C.

SACVD clean investigation with a new calorimetric probe sensor

Doped and undoped SACVD recipes were investigated with respect to their clean performance with a new calorimetric probe sensor. Endpoint curves were collected with a standalone software utility, and results were analyzed post-acquisition offline. The impact of preventive maintenance (PM) activities and different single/multiple cleans towards clean performance were investigated. A numerical model for the clean behavior after annual chamber PMs was developed. Clean time optimization was carried out for different recipes.