NanoFab Trainer Update

Nick Reeder, April 5, 2013

Updates to User Interface

• Replaced look-up tables with graphs when user selects any of the following:– View > Evaporation Deposition Rates– View > Sputter Deposition Rates– View > Dry Etch Rates– View > Wet Etch Rates

• New menu item, Edit > Options, lets user specify the height of the “airspace” displayed above the wafer structure.

Updates to User Interface (Cont.)

• Added new Videos tab that lets user play selected video in a Flash player window.– Requires that user has Flash installed on

computer.

Updates to Thermal Oxidation Code

• Code now correctly handle variations in initial oxide thickness (no longer assumes that the initial oxide thickness is constant over the entire wafer).

Updates to Develop Code

• Implemented two fictional developers:– One removes exposed positive resist at 50 nm/sec,

and has no effect on unexposed positive resist or on other materials.

– The other removes unexposed negative resist at 50 nm/sec, and has no effect on exposed negative resist or on other materials.

• Need to replace with real developers and rates. • Code assumes develop is isotropic, like wet

etch. Is this right?

Photoresist Exposure

• Thinking about how to incorporate Andrew’s C-code algorithm for computing photoresist exposure into the trainer’s polygon-based model.

• Proposal for a simplifying assumption: Since resist solubility changes sharply with DNQ concentration near the solubility threshold, can we simply divide all photoresist into “exposed” and “unexposed” regions after computing DNQ concentration?

Proposal for Photoresist Exposure

– Advantage: Much simpler to model than tracking the DNQ concentration at many points inside the resist.

– Disadvantages: • Inaccurately models development of partially exposed

resist.• Doesn’t model cumulative effect of repeated exposures.

Unexposed Exposed

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