Method of making inverted thin film transistor using backsick exposure and negative photoresist

摘要

A substrate comprising material that is transparent to the radiation used to activate photoresist is selected. A gate electrode is formed on one surface of the substrate. Then an insulating layer and a layer of N+ silicon are deposited, followed by a coating of negative photoresist. The photoresist is now exposed, but the activating radiation is directed to it through the lower surface of the substrate. This results in a mask that allows a gap to be etched in the N+ silicon that is perfectly aligned with the gate electrode. The structure includes a layer of amorphous silicon together with a suitable protective layer and is completed by a conductive layer that is patterned to form connections to other parts of the circuit. The method depends on the transparency of silicon relative to metal so the wavelength of the light used to expose the photoresist must be taken into account.