Robert A. Owen

Uncooled thermal imaging at Texas Instruments

Texas Instruments has developed a new thermal imaging technology based upon focal plane arrays (FPAs) using the pyroelectric effect in ceramic barium-strontium titanate (BST). These devices operate near the paraelectric-ferroelectric phase transition, which, for the selected composition of BST, is near room temperature. The detector elements operate in the voltage mode with a bias voltage applied to maintain and optimize the pyroelectric effect near the phase transition. The BST array attaches via bump-bonding to a CMOS readout circuit that filters, buffers and multiplexes the output signals. These FPAs have facilitated the development of a system technology capable of satisfying a wide variety of applications, including surveillance devices, weapons sights, missile seekers and drivers aids. Resulting systems are performance-competitive with scanned FLIRs in these applications, and they are smaller in size, lighter in weight, and require less power than scanned FLIRs. Simplicity and compactness of the system designs will result in production costs competitive with image intensification devices.

Producibility advances in hybrid uncooled infrared detectors

Several key process developments advance the state-of-the-art in hybrid, uncooled IR detector fabrication. Following a four year producibility roadmap, ion mill reticulation, wafer processing, and standard semiconductor processes are nearing implementation. The discussion describes several proof-of-principle experiments and their results and contrasts the current process approach against an existing, detailed process model. As the thrust continues towards low cost, high volume production, emphasis remains on simultaneous performance improvements. The analyses and preliminary data show that both moderate performance and low detector cost are quite obtainable with the strategies identified.

Producibility of uncooled IRFPA detectors

Demonstrated detectivity of uncooled infrared focal plane arrays is better than O.1°K noise equivalent temperature difference, Uncooled performance levels are now suitable for military and commercial applications. The manufacturing science of this technology lags that for mercury cadmium tellurium based cooled focal planes. The manufacturing issues and approaches for ferroelectric material based uncooled detectors are discussed. The recommended approach is to address producibility issues based on pareto analysis of the process flow and to address the most highly leveraged process steps in terms of time and labor input. Detailed modeling of the process flow has been undertaken as a part of this analysis. Processes addressed in detail are lap and polish of the detector, photolithography, metallization, etches, hybridization, and test. Several approaches are shown to yield comparable cost focal planes, but a process technology leveraging silicon process technologies is shown to minimize space and equipment.