Yong Ruan

INTERFACE STUDIES AND ELECTRONIC PROPERTIES OF SILICON BASED Nd-DOPED BISMUTH TITANATE

ABSTRACT The metal-ferroelectric-insulator-semiconductor (MFIS) structure were fabricated and investigated. The Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on the Si substrates by sol-gel process with HfO2, SiO2 and Si3N4 as the buffer layers. Perovskite crystalline was obtained and the ferroelectric polarization-voltage (P-V) hysteresis was studied for the Pt/BNdT/Pt/Ti/SiO2/Si(100) and Pt/BNdT/HfO2/Si(100) capacitors. Good interfacial properties were examined between the BNdT thin film and Si substrate. Memory windows of the Pt/BNdT/HfO2/Si(100) structure were in the range of 0.9v-1.2v when the thickness of the HfO2 buffer layer varied from 3 nm to 5 nm, exhibiting a considerable memory effect in the capacitors.

MICROSTRUCTURE AND DIELECTRIC PROPERTIES OF ND-DOPED BISMUTH TITANATE

ABSTRACT B3.15Nd0.85Ti3O12 (BNdT) thin films were prepared on Pt(100)/Ti/SiO2/Si(100) substrate by sol-gel process. Perovskite crystalline was observed in the thin films achieved, and the grain size of the thin film was about 200 nm in diameter with sharp and clear boundaries between different films and the Pt electrodes. Well-saturated polarization-voltage (P-V) switching curves were examined in the BNdT thin films. The remnant polarization and the coercive field of the BNdT thin films annealed at 750°C were 43 μ C/cm2 and 66 kv/cm at an applied voltage of 8v, respectively. The dielectric constant and the dissipation factor were 583 and 0.07 respectively, measured at 100 KHz.

Methods to protect silicon microstructures from the damages in deep reactive ion etching

New methods for improving the quality of the silicon deep reactive ion etching (DRIE) procedure were investigated. It suggested that a PECVD oxide layer was deposited at the silicon sidewall and a thermal oxide layer was formed at the silicon backside. Due to the silicon to silicon oxide etching selectivity (120:1-125:1), these oxide layers could protect the silicon microstructures from the damages caused by the lag and footing effects usually occurred in the basic silicon-on-glass (SOG) process. SEM microscope result confirmed that the silicon structure could endure a long time overetch and the structure surface could remain intact by the modified processes. The gyroscope device test results also were in good agreement with new process methods.

High-power mems relay array with improved reliability and consistency

This paper presents a power MEMS relay array with numerous improvements in current-carrying capacity, which adopts silicon-on-insulator (SOI) anodic bonding technology to significantly improve the reliability and consistency of the relay matrix. The relay array is designed as a matrix of microcantilevers connected in parallel to allocate high power to individual relays. This method allows the relay matrix to be configured according to different power requirements. The proposed novel hollow suspended springs ensure that the microcantilevers driven by electrostatic parallel-plate actuators have small driving voltage and high stability.

FABRICATION AND PROPERTIES OF METAL-PZT-METAL CAPACITORS BY LIQUID DELIVERY MOCVD

ABSTRACT Pb(Zr1−x,Tix)O3(PZT) thin films were prepared on 8-inch and 4-inch Pt or Ir-electroded Si wafers by liquid delivery metal-organic chemical vapor deposition (LD-MOCVD) using cocktail sources of Pb, Zr and Ti. The processing conditions were optimized in order to obtain high-performance PZT films. The thickness uniformity of PZT films on 8-inch substrate was about ± 3.24%. The deposition rate of Pb (15.8 nm/min) and Ti (17.9 nm/min) deposited on Si substrate were faster than that of Zr (2.5 nm/min). The growth temperature of PZT film was adjusted to 570–630°C depending on the substrates used. The properties of metal/PZT/metal capacitors were also studied. The PZT films based on Pt substrate showed no good ferroelectric properties. By contrast, the ferroelectric properties of Ir/IrO2/PZT/IrO2/Ir capacitors were excellent. At an applied voltage of 5 V, the remanent polarization (Pr) and coercive field (Ec) values were about 36 μ C/cm2 and 50 kV/cm, respectively.

Vacuum bouncing dynamics dominated by van der Waals forces in MEMS relays

This paper reports a MEMS relay with high reliability, in which van der Waals forces will be used, for the first time, to significantly suppress the vacuum contact bouncing. The dynamic analysis has been carried out by modeling the microcantilever as a multi-segment beam. In the model, van der Waals forces as an adhesive force replace air damping to represent the suppression term. In combination with a dual-pulse actuation waveform implemented by simple logic circuits, the contact bounces were eventually eliminated by making a soft landing.

A New Packaging Method of Alkali Metal Simple Substrate and Related Key Techniques

The vapor cells, which contain the simple substrate of alkali metals, are usually the key part of MEMS atomic devices. Alkali metal is extremely active with oxygen and water, making it incompatible with some necessary MEMS process since the instruments are not oxygen-proof. By using paraffin to packet the simple substrate of alkali metals, rubidium for example, the oxidation and deterioration of the metal can be avoided, making it easier to transfer Alkali metals into the vapor cells. It has also been reported that paraffin can serve as a wall-coating material to improve the Q-factor and the long-term frequency stability of the atomic devices. A mold method of manufacturing the package is introduced along with the related key technologies. Laser beam method and needle mold method are discussed to make blind holes on the paraffin wax layer. Paraffin packages containing rubidium simple substrate has been achieved, ranging from 0.9mm3 to 1.6mm3 in size, with the smallest one containing 0.2μL of rubidium inside. The sealing performance of the package has been tested in a one-month (30 days) test and proves to work well by judging from the color of the sealed metal. A low-temperature anodic bonding process is introduced for the fabrication, and absorption spectrum of the vapor cell is obtained, proving that alkali metal simple substrate has been transferred to the vapor cells.

Comparison of PbZr1−xTixO3 thin films deposited on different substrates by liquid delivery metal organic chemical vapor deposition

In the paper, PbZr1−xTixO3 (PZT) thin films were prepared on different substrates including 8 and 4 in. silicon, Pt, Ir, and IrO2/Ir substrates by liquid delivery metal organic chemical vapor deposition. Through optimizing the preparation condition, the better film uniformity of thickness, composition, and temperature was achieved. The thickness uniformity of PZT films on 8 in. substrate was about ±3.24%. The deposition rate of Pb (15.8 nm/min) and Ti (17.9 nm/min) were much faster than that of Zr (2.5 nm/min). The growth temperature of PZT film was 570–630 °C depending on the substrate used. The growth rate of PZT films deposited on Si (30–35 nm/min) was faster than that on metal substrate. The substrate has a great effect on the ferroelectric properties of PZT films. PZT film growing on Ir was much uniform and denser than that on Pt, highlighting the good microstructure achieved. PZT films based on Ir substrate showed excellent ferroelectric properties. At the applied voltage of 5 V, the remanent polari...