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.• 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 for CVD based 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.

Activity Not started Partial Complete

Simulation coding

Clean X

Spin coat X

Bake X

Mask/Expose/Develop X

Evaporate X

Thermal oxidation X

CVD X

Sputter X

Wet etch X

Dry etch X

Lift off X

Polish X

Implant X

Track time, cost, quality of each process X

User -interface coding

History with option to revert X

Save/open history files X

Edit colors X

User-defined materials X

Profilometer X

Producing embedded media (videos, photos, etc.) X

Testing X

Documentation X