No abstract

This paper presents a three-dimensional microfabrication and integration technology for MEMS smart materials that utilizes a spray coating method. Spray coating is shown to be most effective for additional deposition on non-planar surfaces. PZT films were formed both on flat and uneven surfaces at a thichess of about lpm. Perovskite structures were formed with suitable heat treatment and ferroelectric P-E hysteresis loop was also obtained. This paper is the first report from our group and other researchers on the deposition of smart materials for MEMS using a spray coating method. Spray coating has been proposed as an effective threedimensional coating method which can be used to deposit piezoelectrics, pyroelectrics, magnetics,'etc. for sensors and actuators. The hydrophilic and hydrophobic . ' ' properties between the substrate surface and ejected liquid are most essential process factors in the spray coating method for improving the film growth conditions.

This paper presents a three-dimensional microfabrication and integration technology for MEMS smart materials that utilizes a spray coating method. Spray coating is shown to be most effective for additional deposition on non-planar surfaces. PZT films were formed both on flat and uneven surfaces at a thickness of about 1 lm. Perovskite structures were formed with suitable heat treatment and ferroelectric P-E hysteresis loop was also obtained. This paper is the first report from our group and other researchers on the deposition of smart materials for MEMS using a spray coating method. Spray coating has been proposed as an effective three-dimensional coating method which can be used to deposit piezoelectrics, pyroelectrics, magnetics, etc. for sensors and actuators. The hydrophilic and hydrophobic properties between the substrate surface and ejected liquid are most essential process factors in the spray coating method for improving the film growth conditions. IntroductionConventional large scale integration (LSI) fabrication technologies have been developed mainly for flat surfaces, e.g. Si-wafers. However, there have been an increasing demand for three-dimensional manufacturing techniques to create devices with highly integrated and complicated structures; e.g high aspect ratio structure and step-coverage structure for ferroelectric memory. It is thus necessary to develop a new fabrication technology for deposition onto etched base plates, curvature substrate and stepped and cylindrical surfaces. Rapid prototyping and low-temperature integration are also important process factors for this technology. Chemical solution deposition (CSD) could be useful for forming smart materials except for its step coverage, while chemical vapor deposition (CVD) is suitable for the step coverage but is inadequate for many other process factors at present. Therefore, a spray coating method, Sasaki et al [1] is considered to be effective for these purposes. Spray coating system is originally developed as a resist coating onto non-planar surface; e.g. bonding surface of optical fiber. Spray coating involves ejecting fine liquid particles of smart materials by a jet stream of carrier gas onto the substrate. Spray coating has advantages both in the high-quality formation of chemical solution deposition and also in three-dimensional fabrication including step coverage coating. It is also possible to use spray coating for additional deposition onto deepetched base plates, and coating onto cylindrical non-planar surfaces and micromoldings. Spray coating enables the formation of the structure in both dry and wet conditions by controlling the deposition process conditions. It is also important to control the solution concentration to adjust the hydrophilic or hydrophobic properties with the substrate. Spray coating with electrostatic force has been proposed for film formation [2-3] but cannot be as used widely as spray coating without electrostatic force (our approach). Gas-deposition[4-6], which is a dry deposition process that uses fine par...

No abstract

No abstract