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Unformatted text preview: Unit 5: Lithography Using photoresists: o Traditional: +ve resist becomes soluble when exposed to light First put down mask, then dissolve, then etch o Lift-off: put photoresist down first, then dissolve Dont have to etch metal itself, using solvent to do patterning so its easier Depositing on photoresist (polymer) so need low temps (cant burn photoresist), cant use regular CVD process o Aerial image: 2D optical pattern received in the water at the photoresist o Latent image: 3D pattern in photoresist after exposure and development Why use fused silicon for mask blank? o Quartz- only glass that has transmission in UV range, most other glasses will absorb UV Contact printing : high resolution since less distance for diffraction but high defect densities o R = Projection printing : high resolution than proximity, low defect densities, dominates today, more complicated system, intrinsic ability for demagnification using optical system (scaling advantage), good...
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- Spring '11