P1. Positive pattern transfer with lift-off.
     First step of the work will be done with positive tone resist characterization as electron sensitive material and as a mask support during pattern transfer. Another resist properties characterization will be focused on thin film thickness as a function of its viscosity, spinning angular velocity and its roughness changes after each processing step. Students will be asked to characterize positive e-beam resist by its sensitivity, contrast, process window and its spin curves. Double layer coating will be explained as a method for achieving the necessary undercut when lift-off is to be used.
     Second step will be the e-beam lithography method. This will involve full turn with data preparation from 2D layout coding down to internal JEOL format conversion and job control files creation. Some aspects of the e-beam method in terms of e-beam writing conditions and system calibration will be discussed. An e-beam exposure will follow.
     Third step will be the resist development with addressing some aspects of post exposure baking, especially for the case when CAR ( chemically amplified resists ) are used. Process window definition will be introduced and discussed with factors influencing its shape. Optical microscopy inspection will be done with discussion of how polarized light method can be used for better undercut evaluation.
     Fourth step will cover PVD thermal evaporation method with its physical aspects of process optimization.
     Fifth step will be spent on lift-off, with emphasis on optimal process conditions. Final inspection with optical microscopy and SEM topographical measurements will conclude the experimental part of the project.
     Bonus assignment ( for ambitious students ) will be based on plasma etching of the substrate with the thin metal film resulting from lift-off as a etching mask. Several aspects of the etching chemistry and its selectivity will be addressed.

Piotr Jedrasik