Development of a micromachined electrode array for cochlear implant application is presented. The device is constructed from a silicon substrate with sputtered platinum electrodes and connection tracks. Electrochemical impedance spectroscopy (EIS) is used to study the properties of the electrode, and to identify potential problems caused by the micromachining process and materials. A variety of insulators are studied and a two part epoxy is identified as an adequate insulator for operation under harsh electrochemical testing conditions. The semiconducting silicon substrate is found to contribute to the total impedance of the device at high frequencies due to the thin insulating oxide between the substrate and conducting tracks. This is a potential problem for micromachined electrodes operating under high frequencies or using square stimulating pulses. The charge-delivery properties are studied using electrochemical impedance spectroscopy. It is found that platinum sputtered under particular conditions results in excellent surface conditions for optimum charge-delivery.
Progress is reported on the development of uncooled microbolometer IR focal plane detector arrays (IRFPDA) under a research collaboration between the Swedish Defence Research Establishment (FOA), and the Defence Science and Technology Organization (DSTO), Australia. The paper describes current focal plane detector arrays designed by Electro-optic Sensor Design (EOSD) for readout circuits developed by FOA. The readouts are fabricated in 0.8 micrometer CMOS, and have a novel signal conditioning and 16 bit parallel ADC design. The arrays are post-processed at DSTO on wafers supplied by FOA. During the past year array processing has been carried out at a new microengineering facility at DSTO, Salisbury, South Australia. A number of small format 16 X 16 arrays have been delivered to FOA for evaluation, and imaging has been demonstrated with these arrays. A 320 X 240 readout with 320 parallel 16 bit ADCs has been developed and IRFPDAs for this readout have been fabricated and are currently being evaluated.
The performance of uncooled infrared focal plane detector arrays depends on optimization of critical parameters which are determined by geometrical design and the electrical, optical and thermophysical properties of the detector materials. It is desirable to monitor these parameters during array preparation using test cells which are independent of the main array and which can subsequently be used to provide data for performance analysis. This paper describes the use of test structures which function as process control modules and monitor cells for material parameters, from which array operability and performance can be assessed. The focal plane detector arrays described in the paper were designed by Electro-optic Sensor Design and manufactured by the Defence Science and Technology Organization, Australia, in collaboration with the Defence Research Establishment, Sweden.
This paper reports on the development of silicon microbolometer uncooled IR focal plane detector arrays at the Defence Science and Technology Organization (DSTO), in collaboration with the National Defence Research Establishment (FOA). The detector arrays were designed by Electro-optic Sensor Design, which also provided specialist scientific advice on array fabrication. Detector arrays are prepared by monolithic processing at DSTO, using surface micromachining to achieve thermal isolation, and are integrated on-chip with a CMOS signal conditioning and readout microcircuit designed by FOA. The CMOS circuit incorporates 16-bit analog-to-digital conversion, and is described in more detail in an accompanying paper presented. The ultimate objective is to develop 'smart' focal plane arrays which have on-chip signal processing functions, giving a capability for decision making such as automatic target detection. The silicon microbolometer technology described in the paper was invented at DSTO, and is representative of core technology employed in many initiatives world-wide. A brief overview will be given of theoretical considerations which influence detector array design, followed by an outline of recent developments in array processing.
This paper discusses the development of a high resolution digital readout from a 2D array of uncooled IR detectors. The need for a high resolution analogue to digital converter (ADC) is described and anew concept is presented. Experimental VLSI arrays have been designed using 0.8 micrometers CMOS technology and the pixel size is 40 micrometers X 40 micrometers . The concept has been demonstrated by using 320 parallel 16 bit ADCs in a 320 X 240 readout array with a frame rate of 30 Hz. High linearity and low noise is obtained and the power consumption for each ADC is 0.5 mW. The high digital resolution allows for digital offset correction off the local plane. A 16 X 16 version of the readout circuit has been postprocessed with uncooled IR detectors. These are currently under evaluation.
This paper presents an overview of the research program on uncooled IR sensitive bolometer technology at the Defence Science and Technology Organisation (DSTO). It covers the design, materials growth, and performance of semiconductor film bolometer (SFB) IR detectors, with a strong emphasis on the practical considerations involved in their production. The overview includes a discussion of thermal isolation and the effects that vacuum packaging, and other alternative technologies, have on the performance of the detectors. Some of the principal applications of uncooled SFB IR detectors are also discussed. Finally, current technological developments in the DSTO uncooled sensor program and the direction of future research are described.
This paper describes the growth and properties of micro-machined semiconductor microbolometers. These thermally isolated structures are employed in uncooled infrared detectors developed at the Defence Science and Technology Organisation (DSTO). Recent research is focused towards developing high performance bolometers from the amorphous and more recently the microcrystalline phases of the SiGe:H material system. Particular attention is given to materials and material growth techniques that maximize the responsivity and minimize the electronic excess noise. The basic design, materials science, and performance of these bolometers for detecting infrared radiation are described in this paper.
This paper discusses the design of monolithic thin film thermal detectors, with particular reference to the parameters which influence performance such as thermal conductance. Methods for implementing thermal isolation are described, and critical fabrication technology is outlined. Optional materials technology for thin film resistance bolometers is reviewed, and consideration is given to bias and signal conditioning techniques.