MEMS technology, derived from the microelectronics industry, has enabled the manufacture of high volume sensors and actuators. However, the technology path for standard CMOS technology is smaller geometries, planar topology, and lower thermal budgets, while MEMS process technology have been moving towards high aspect features, high thermal budgets and non-aggressive lithography requirements. This has important implications for the viability of MEMS to be a mainstream technology that can support the products of a new generation of products and applications. This paper will review some of the emerging trends in MEMS technology and discuss some of the applications. The challenges in ensuring the manufacturing viability of MEMS technology will also be briefly discussed.
Wet etch processes are important for the production of MEMS devices. Sacrificial oxides are often used to help define polysilicon structures, and these films are often etched using solutions containing hydrofluoric acid. One important consideration is the use of an etch stop which is resistant to HF. In this study, a silicon-rich silicon nitride film was developed for this purpose. Process parameters such as DCS:NH3 ratio, pressure and temperature have ben varied in order to create a film that has a low wet etch rate, good cross-wafer and cross-load uniformity, and low conductivity for good isolation resistance. The film is also designed to have a low tensile stress, which should minimize etch rate and also minimize wafer curvature, which is beneficial for subsequent photo steps. Finally, film characterization using the index of refraction as the primary process control is discussed.
Polysilicon is the most commonly used film for surface micromachined devices such as accelerometers, gyroscopes, and pressure sensors. In this study, the development of implanted polysilicon film s for surface micromachined devices is reported. These devices were developed for integration with a double level metal sub micrometers CMOS product line. For films with 5-30 k angstrom thickness, and residual stress, sheet resistance, deposition rate, and thickness uniformity were characterized as a function of deposition temperature, silane flow rate, implant dose, and anneal conditions.
An alternative non-destructive analysis method using laser scanning microscopy (LSM) was used to study etch release distances in MEMS pressure sensor. The LSM method eliminates samples preparation and is easy to implement in a MEMS manufacturing environment. In this study, various diaphragm structures were etched using a highly concentrated HF based solution. Experimental etch data were obtained for both SiO2 and PSG films under these various structures. Both the height and the width of the sacrificial layer port/channel had a significant effect on etch rate for both films. As expected, a non-linear etch rate was obtained for both SiO2 and PSG films. Since the HF concentration changes over time in a manufacturing bath process, careful selection of processing time is required in order to fully release MEMS structures. Future theoretical modeling with the assistance of experimental data obtained in this study is being pursued to strengthen past work done by Eaton et al, Monk et al, and Liu et al.
This paper looks at the issues related to the integration of pressure sensors with the control circuit necessary to achieve the demands of increased performance measured by such parameters as linearity, resolution, accuracy and temperature sensitivity. In addition, the media in which these devices are used can influence the performance considerably with attendant offsets and drifts. Results of the effects of the media exposure on capacitive pressure sensors are presented. The motivation for integrating the sensor with the control circuit is then discussed with respect to these experimental results.
We have developed a method to pattern self assembled monolayer films of n-octadecyltrichlorosilane on silicon and glass substrates using a simple lift-off procedure. By defining hydrophobic regions at definite locations in microchannels and using an external pressure source, we can split off precise nanoliter volume liquid drops and control the motion of those drops through the microchannels. We have also constructed an on-chip pressure source for drop splitting and motion by heating air trapped in a micromachined chamber. Both techniques can produce and move drops on the order of 50 nl.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.