P3. Ebeam lithography and its patterning fidelity limits by proximity effects.
    First step of the work will be done with positive and negative tone resist characterization as electron sensitive material and as mask support during pattern transfer by chrome etching. Another resist 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.
     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. Inherent critical dimension distortions resulting from both, inter- and intra-proximity effects will be explained. Three different layouts will be prepared and exposed. First, acting as an example for showing the severity of the electron scattering thus qualitatively presenting the proximity effects. Second one will be prepared to calibrate and evaluate the model of the proximity function by double Gaussian distributions. This will be used as initial pre-compensation condition parameters for distortion less mask production. The last, third one will be used for accurate resist contrast measurements. Necessity of this data for the process calibration in terms of layout feature lateral dimensions in the light of the resist development threshold level will be explained.
    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 feature size evaluation.
    Fourth step will cover PVD thermal evaporation method with its physical aspects of process optimization. In this case the evaporated film will be used as a resist stabiliser for SEM inspection.
     Fifth step will be spent on SEM topographical measurements, which will conclude the experimental part of the project.
     Bonus assignment ( for ambitious students ) will be based on calculation and modeling the proximity function and the implementation of the results for the layout geometry pre-compensation. Finally, an evaluation exposure will be performed to estimate the correctness of applied proximity effects correction.

Piotr Jedrasik