Fabrication and modelling of porous silicon schottky diode
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The thesis work primarily focuses on fabrication and modelling of Schottky Diode formed using porous silicon. The wafer used for this is silicon coated with silicon nitride on both sides. A photoresist is deposited on the front side of the wafer using spin coating technique and silicon nitride that is coated on the back side is etched off using dry chemical etching process. A photomask is designed using AutoCAD software which helps open windows on the front side of the wafer. Windows are opened on the front side using positive photoresist technique. This technique enables the portion of the wafer that is exposed to UV light more soluble in the developer solution making the unexposed portion opaque or insoluble. Silicon nitride is etched off on the front side where the windows are opened using similar dry chemical etching process. After coating photoresist on the front side, silicon nitride on the backside is etched completely. Silicon nitride thickness before and after etching has been recorded. The wafer is then diced into smaller samples and allowed to grow pores. Electrochemical etching process with the electrolyte HF:Ethanol in the ratio of 1:3 is used for porous silicon formation. The samples are then coated with Chrome/Gold contact on front and backside and are examined under Scanning Electron Microscope (SEM). The device, when exposed to light, exhibits schottky diode characteristics. The forward and reverse diode characteristics have been tested.