Block Engineering: MEMS Technology Overview
Our patent pending MEMS miniaturization technologies are enabling breakthrough new products, like the ChemPen™, a pen-size, battery-operated FTIR sensor which can detect essentially any gas, liquid or solid.
Block's strategy is similar to today's "Intel Inside" model, under which Block's unique MEMS "chips" would become the "engines" inside handheld-type devices that could analyze substances both inside and outside the traditional laboratory settings. Block's value proposition is small size and very low cost.
This revolutionary concept of "Mobile Instrumentation" will create a new generation of small, low cost sensors that still offer high functionality. The concept is similar to today's cell-phones/PDAs or laptops computers, which have revolutionized the fields of Mobile Communications and Mobile Computing with increasingly low cost/high functionality capabilities.
ChemPen: Point Gas Sensor
Block is currently developing the ChemPen (conceptual drawing shown in figure), which incorporates well established and tested Fourier Transform Infrared (FTIR) spectroscopy. It is software programmable to detect virtually any gas except the diatomic molecules (oxygen, nitrogen, etc.) and with appropriate accessories can also detect liquids and solids. It performs the same function as larger broadly used FTIR analytical instruments – i.e. to detect, identify and quantify substances in labs, industrial processes and many other applications.
Its small size (8 inches), low weight (8 oz), low power consumption and expected very low cost gives it a high value proposition versus competing products. The ChemPen interferometer is being built using a very sophisticated MEMS fabrication process, SUMMiT-V, developed by Sandia National Laboratory.
The ChemPen Sensor is intended to detect and identify all Chemical Warfare Agents and Toxic Industrial Chemicals under field conditions. Target markets: Military, Homeland Security, Life Safety
MEMS Technology/Market Overview
Microelectromechanical systems (MEMS) are small integrated devices or systems that combine electrical and mechanical components. They range in size from micron (thousandth of a millimeter) to millimeter level, and a complete system could contain a few or thousands of such components. MEMS extend the fabrication techniques developed for the integrated circuit industry to add mechanical elements such as beams, diaphragms, springs and, even motors, gear drives and other similar moving structures.
Examples of MEMS device applications include inkjet-printer cartridges, accelerometers, miniature robots, micro-engines, locks, inertial sensors, micro-transmissions, micro-mirrors, micro-actuators, optical scanners, fluid pumps, transducers, and chemical, pressure and flow sensors. New applications are emerging as the existing technology is applied to the miniaturization and integration of conventional devices.
These systems can sense, control, and activate mechanical processes on the micro scale, and function individually or in arrays to generate effects on the macro scale. The micro fabrication technology enables fabrication of large arrays of devices, which individually perform simple tasks, but in combination can accomplish complicated functions.
MEMS is not limited to a single fabrication process or a few materials, which enables the development of numerous and diverse devices and applications, by selecting the appropriate fabrication process and material. The MEMS industry had reached $6.5B in 2009 and is expected to grow to $16B by 2015.
MEMS Fabrication typically combines innovations and techniques that fall into the following categories:
- IC Fabrication: The traditional techniques of film growth, doping, lithography, etching, dicing, and packaging are used extensively in the MEMS industry.
- Bulk Micromachining and Wafer Bonding: Bulk micromachining is an extension of IC technology for the fabrication of 3D structures. Bulk micromachining of Si uses wet- and dry-etching techniques in conjunction with etch masks and etch stops to create micromechanical devices from the Si substrate.
- Surface Micromachining: Surface micromachining enables the fabrication of complex multicomponent integrated micromechanical structures that would not be possible with traditional bulk micromachining. This technique utilizes layers of sacrificial material during the fabrication process. Using the substrate wafer as mechanical support, multiple layers are deposited and patterned to create the desired micro-structures. Subsequent chemical etching dissolves the sacrificial layers and forms the final structures. One of the most widely used technique, is polysilicon surface micromachining, in which polysilicon is the structural material.
- LIGA Process: LIGA is a German acronym standing for "Lithographie, Galvanoformung und Abformung" (Lithography, Electroplating, and Molding). This process can be used for the manufacture of high-aspect-ratio 3D microstructures in a wide variety of materials, such as metals, polymers, ceramics, and glasses. In difference to the bulk and surface micromachining, this technique uses a selective deposition process, typically a plating process, to deposit the material at predetermined locations.
The above mentioned applications range from fairly simple, commodity-type MEMS devices, such as accelerometers, or inkjet-printer cartridges to very sophisticated, complex devices, such as the ChemPen being developed by Block. For such devices, a unique Surface Micromachining process is used, called Ultra-planar, Multi-level MEMS Technology 5 (SUMMiT V™), developed by Sandia National Labs. The process allows the formation of five layers and has led to some very impressive devices with both moving and stationary components.
"High-resolution miniature FTIR spectrometer enabled by a large linear travel MEMS pop-up mirror," Erik R. Deutsch, David Reyes, Elliot R. Schildkraut, and Jinhong Kim, Proc. SPIE, Vol. 7319, 73190J (2009) [pdf]
"A novel method of creating a surface micromachined 3-D optical assembly for MEMS-based, miniaturized FTIR spectrometers," D. Reyes, E. R. Schildkraut, J. Kim, R. F. Connors, P. Kotidis, and D. J. Cavicchio, Photonics West, January 2008 [pdf]
"A MEMS based absorption micro-spectrometer for toxic vapor detection and identification," E. Robert Schildkraut, David Reyes, Dr. Daniel J. Cavicchio, Dr. James O. Jensen; Passive Standoff Detection Team, U.S. Army ECBC, Aberdeen Proving Grounds, November 2006 [pdf]