The design, numerical modelling and development of MEMS fabrication process of micro bolometer for use in long wave infrared detection.

Abstract

The Advanced Manufacturing Technology Strategy (AMTS), predecessor of the Technology Innovation Agency, was a national strategy focused principally on improving collaboration amongst industry, academia and science councils. The aerospace industries and training institutions in particular have been identified as key thrust areas for achieving economic development through the AMTS. Furthermore, the AMTS Aerospace Interest Group has been identified as one of the most important facets of Micro and Nano Manufacturing, Sensors and Electronics Flagship Program. The manufacturing of Micro and Nano Electronics and sensors is essential for South Africa to sustain the technology capability development as seen in developed countries. For example, there is an urgent need to establish a Photo Lithography facility for South African industry and training Institutions. The demand for the new generations of industrial, military, commercial, medical, automotive and aerospace products in South Africa in particular, and in the world in general, has fuelled research and development activities focused on advanced and smart materials. This situation has allowed for the emergence of a new generation of infrared sensors, the bolometer, based on an infrared thermal detection mechanism which is particularly suited to operate at ambient temperature, opening opportunities for achieving low cost infrared imaging systems for both military and commercial applications. This work deals with different South African bolometer membranes of the second prototype in collaboration with the University of Pretoria and Denel Optronics. The bolometer is an infrared thermal sensor that measures thermal radiation by converting said radiation into a temperature change and subsequently measuring the induced change in electrical resistance. The term infrared from Latin Infra, meaning below, is usually applied to wavelengths between 700nm and 1mm. It can be argued that the first occurrence of infrared sensing actually goes back several millennia, when men placed their hands over recently extinguished fire. However, until Herschel’s experiment, this kind of infrared was between the sun and the earth. Thermal imaging, which refers to the ability to measure the temperature of different points on a scene, requires either an array of infrared detectors operating in those wavelength ranges or a way to scan a scene using a single detector. To realise this work, objectives have been assigned to different groups of the consortium represented by CPUT, UP and Denel. Analyses of thirteen bolometer membranes including metal bolometer (Titanium) and Vanadium oxide were assigned to CPUT, reason why this thesis focuses on the modelling, designing and testing of the bolometer membranes. Masks design of the second prototype bolometer test structures includes several thermally isolated bolometer devices. These devices have been modelled and analysed in order to study their electrical and thermal behaviour.