Please answer question 2b. If you are writing by hand pleasemake handwriting as readable as possible.
2. Lithography:
(a) Polymers containing aromatic rings are more likely to absorb UVphotons, leading to chain scission. Would this make them negativeor positive resists for lithography. (2 points)
(b) Explain briefly how lift off works. (2 points)
(c) Explain why chips are exposed with a stepper (so only asmall field of view is illuminated at a time) in deep UVlithography? (2 points)
(d) Looking at the electron trajectories in Fig 5.8.explain whyit would be useful to have a resist with a fairly sharp thresholdexposure needed to make it soluble. (2 points)
(e) It is desired to etch away the whole thickness of a siliconwafer with a well- defined etch angle. How can this be achieved? (2 points)
