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NanoFab Trainer Update. Nick Reeder, March 1, 2013. Updates to User Interface. When starting the program or starting a new file, user is now prompted to specify the width of the design. This width is saved when saving work to file, and is restored when opening an existing file.
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NanoFabTrainer Update Nick Reeder, March 1, 2013
Updates to User Interface • When starting the program or starting a new file, user is now prompted to specify the width of the design. • This width is saved when saving work to file, and is restored when opening an existing file. • Height of display window is now auto-scaled to show two microns above top of wafer structure (unless user has selected View Equal Horizontal and Vertical Scales).
Updates to User Interface (Cont.) • To improve readability, added units and background color to look-up tables when user selects any of the following: • View > Evaporation Deposition Rates • View > Sputter Deposition Rates • View > Dry Etch Rates • View > Wet Etch Rates
New Code: Combining Layers • New code combines adjacent layers of the same material. • Need this to correctly handle processes that depend on total layer thickness, such as thermal oxidation and UV exposure of photoresist.
Updates to Thermal Oxidation Code • SiO2 now grows down into the Si (45%) and upward from the original surface (55%). • Assumption: Si is oxidized to SiO2 only where either Si is exposed to the surface, or Si is directly under a layer of SiO2 that is exposed to the surface. A layer of any other material above the Si or SiO2 prevents oxidation.
Updates to Thermal Oxidation Code (Cont.) • Uses Deal-Grove model to compute oxide thickness based on time, temperature, initial oxide thickness, and environment (wet or dry). Assumes <100> crystal orientation. Checked against online calculator at BYU. • Not fully functional; it works if the initial oxide thickness is constant over the entire wafer, but doesn’t correctly handle variations in initial oxide thickness. • View > Oxidation Rate Curves lets user see effect of varying the input parameters.
To-Do List • Implement look-up tables to compute deposition rates forCVDbased on user-supplied pressure & temperature. • Populate evaporation and sputter look-up tables with values. • Fix expose,develop, polish code to compute depth from user-supplied values. • Continue writing bake code; need realistic values for S0 and . • In expose code, implement diffraction of UV in air and absorption within resist, with dependence on solvent content from bake code. • Fix etch code so that (for photoresist) etch rates depend on solvent content from bake code. • Fix spin-coat code so that resist does not adhere to underside of horizontal surfaces. • Write new code for • Lift-off • Clean • Profilometer • Write time-cost-quality code for all operations. • Write online help text. • Produce videos, photos, text for Tutorial tab.