Lawrence A. Goodman

High-sensitivity uncooled microcantilever infrared imaging arrays

The structure and operation of a new uncooled thermal infrared imaging detector is described which is composed of bimaterial, thermally sensitive microcantilever structures that are the moving elements of variable plate capacitors. The heat sensing microcantilever structures are integrated with CMOS control and amplification electronics to produce a low cost imager that is compatible with silicon IC foundry processing and materials. The bimorph sensor structure is fabricated using amorphous hydrogenated silicon carbide (a-SiC:H) as the low thermal expansion coefficient material, and gold as the high thermal expansion coefficient bimaterial (14 x 10-6/K). Amorphous hydrogenated silicon carbide is an ideal material in this application due to its very low thermal conductivity (0.34 W/m-K) and low thermal expansion coefficient (4x10-6/K). High resistivity (200-400 Ω/sq) thin Ti/W films are used as the infrared resonant cavity absorber and low thermal loss electrical interconnect to the substrate electrical contacts. A temperature coefficient of capacitance, ΔC/C, (equivalent to TCR for microbolometers) above 20% has been measured for these structures, and modeling of the performance of these devices indicates sensor performance in the range NETD < 5 mK and thermal time constants in the 5 -10 msec range are feasible with this technique. Our development efforts have focused on the fabrication of 320 x 240 imaging arrays with 50 micron pitch pixels. A number of these arrays have been fabricated with performance characteristics that are predicted by a detailed thermo-electro-optical-mechanical model of the sensor. The sensor design and the results from measurements of the thermo-electromechanical and optical properties of the detector arrays will be discussed.

Progress toward an uncooled IR imager with 5-mK NETD

The bi-material concept for room-temperature infrared imaging has the potential of reaching an NE(Delta) T approaching the theoretical limit because of its high responsivity and low noise. The approach, which is 100% compatible with silicon IC foundry processing, utilizes a novel combination of surface micromachining and conventional integrated circuits to produce a bimaterial thermally sensitive element that controls the position of a capacitive plate coupled to the input of a low noise MOS amplifier. This approach can achieve the high sensitivity, the low weight, and the low cost necessary for equipment such as helmet-mounted IR viewers and IR rifle sights. The pixel design has the following benefits: (1) an order of magnitude improvement in NE(Delta) T due to extremely high sensitivity and low noise; (2) low cost due to 100% silicon IC compatibility; (3) high image quality and increased yield due to ability to do offset and sensitivity corrections on the imager, pixel-by-pixel; (4) no cryogenic cooler and no high vacuum processing; (5) commercial applications such as law enforcement, home security, and transportation safety.

34.4: High Performance CMOS‐on‐Plastic Circuits using Sequential Laterally Solidified Silicon TFTs

We developed a CMOS-on-plastic technology using sequential lateral solidification to form LTPS TFTs. We have achieved unity-gain frequencies ft greater than 250 MHz, with CMOS ring oscillators operating at 100 MHz. To our knowledge these are the highest frequency transistors and circuits ever fabricated directly on plastic.

100 MHz CMOS circuits using sequential laterally solidified silicon thin-film transistors on plastic

We have fabricated CMOS circuits using sequential laterally solidified silicon TFTs on plastic substrates. NMOS devices have unity-gain frequencies greater than 250 MHz, and CMOS ring oscillators operate at 100 MHz. To our knowledge these are the highest performance transistors and the fastest circuits ever fabricated directly on plastic

CMOS-on-Plastic Technology using Sequential Laterally Solidified Silicon Thin-Film Transistors

CMOS circuits are directly fabricated on plastic substrates using a process with a maximum temperature of 300degC. NMOS transistors with 2mum channel lengths have unity-gain frequencies greater than 250MHz, and CMOS ring oscillators operate at 100MHz with a 15V supply