MEMS program at Sinapores Institute of Microelectronics

11/01/1998

MEMS program at Singapore`s Institute of Microelectronics

Jason Lim, Institute of Microelectronics, Singapore

The Institute of Microelectronics (IME), Singapore, is a multidisciplinary research institute specializing in core areas of microelectronics. The mission of this applied R&D organization is to help nurture microelectronics industries in Singapore. One of the application areas IME has chosen to develop is the industrially important field of microelectromechanical systems (MEMS). IME has been working closely with several multinational companies to bring MEMS products to the industry.

Silicon-based MEMS devices can be mass-produced at a low cost. These devices are used extensively in automotive, medical, process control, data storage, and military applications. IME has developed a total set of capabilities for MEMS, from concept to manufacturing, by leveraging its expertise from IC fabrication, ASIC design, packaging, and reliability analysis. IME has also developed extensive MEMS modeling capabilities.

IME has a core MEMS applications group that interacts with customers and with its own microelectronics process technology, VLSI design packaging, and failure analysis departments. IME`s engineers design, fabricate, package, and test MEMS devices. IME has developed several capabilities in both bulk and surface micromachined MEMS devices, and developed cost effective ASICs for signal conditioning and prototype packages.

Single crystal silicon-based MEMS devices like pressure and acceleration sensors are of great industrial importance. IME has designed and fabricated such sensors successfully over the past three years. We have developed ultra- stable piezoresistive technology for pressure sensors, and have also developed and transferred to industry a highly successful accelerometer based on single-crystal silicon (see figure). This accelerometer uses low-cost IC processing and single crystal silicon for mechanical and electrical elements. IME developed a proprietary trench isolation process in order to make this feasible, using low cost silicon substrates. In the process of developing these technologies, IME engineers have accumulated a valuable set of micromachining processes and designs that can be used to fabricate various micromechanical structures like microphones, microrelays, and micromirrors.

Modeling of micromechanical structures is necessary for designs to meet product specifications. IME has modeling capabilities for MEMS such as MEMCAD, ANSYS, MATLAB, Matchcad, and SABRE. These are used effectively to interface MEMS designs with IC layout and modeling CAD software like SPICE and CADENCE in order to understand coupled electrical, mechanical, and thermal effects. This has proved to be of value in modeling.

One of the key factors for commercial success of MEMS devices is the ability to signal condition the weak output of MEMS devices. IME has experience in mixed signal CMOS circuitry that can be used to amplify and calibrate. Our electronic trimming capability has enabled cost effective packaging followed by trimming using fusible-link techniques. Previously, the most popular technique to calibrate MEMS devices has been to laser trim the ASIC circuitry. This procedure needs expensive test setups and transparent packages or semi-packaged MEMS for the laser to access trim resistors. Most mechanical MEMS devices are sensitive to temperature and package-induced stress, for which laser trimming has been a costly process. By fully packaging MEMS devices and ASICs, and then electronically trimming and calibrating the ASIC wired to the MEMS device, IME has demonstrated competitive ways of mass producing MEMS products.

In addition to these activities, IME has ongoing programs in infrared uncooled bolometer arrays, scanning cantilever probes, microphones and microrelays for low- and high-frequency applications. IME constantly looks for suitable industrial partners in or outside Singapore to collaborate on these projects. IME hopes to make Singapore a leading manufacturing base of MEMS products and spin-offs.