Optimization studies of lift-off methods and its application in electrochemical biosensors

Increasing demand for faster and more accurate diagnostic procedures has sparked trends in the development of electrochemical sensors for biology research and medical diagnostics. Inter-digitated electrode based electrochemical sensors have shown higher sensitivity and label-free approach to medical diagnostics. This paper presents a comparative study on the different lift-off methods which were used in the fabrication of high density gold inter-digitated electrodes (IDE) for electrochemical detection. The paper focuses on the generation of “T-Topped” resist profile also known as re-entrance resist profile which facilitates efficient metal lift-off after deposition. IDE with thickness of 30nm Ti and 200nm gold electrodes with 5μm line width and a pitch of 15μm were patterned on an 8” silicon substrate insulated with thermal oxide film. The detailed fabrication processes, the adhesion enhancement strategies, and accounts for the merits and limitation of each proposed fabrication technique are presented. Lastly, the impact of different expose dose on the final critical dimension (CD) of the electrochemical sensors was investigated.