Development of photochemical etching and its application in fabrication of integrated reflector metal semiconductor metal photodetectors

Photolithography and etching form the basis of any microfabrication process. Consequently, there is a lot of interest in the research community to improve and innovate on these crucial steps so as to realize the fabrication of complex devices. Once limited to use as physical photomasks for producing planar features, photolithography and etching are now being expanded to function with virtual programmable masks and to produce complex non-planar structures. These "3-D" structures are of great interest in fields like photonics, microfluidics and microelectromechanical systems (MEMS). A number of competitive solutions have been proposed to enable this "grayscale" processing of materials. This thesis discusses digital projection photochemical etching as a possible tool for maskless, grayscale lithography and etching in a single step. It is based on light-assisted etching of semiconductors placed in a suitable chemical solution. By projecting spatially varying intensity light, grayscale etching can be achieved. The thesis begins with the motivation and literature review of this area of study, and then discusses the fundamental mechanisms of the photochemical etching process. Finally, an application of the fabrication of high-responsivity metal-semiconductor-metal (MSM) photodetectors is discussed to show how photochemical etching can be integrated with conventional microfabrication to enhance device fabrication capability