TRACER

TRACER is part of the BEAMER software package.

Using TRACER you can calculate a point spread function (PSF) for your specific substrate and material stack. It is done by defining material layers and running a Monte Carlo simulation for a large number of electrons. The result can be exported for use in Beamer PEC.

Website

How to: make a PEC for a new material stack

This is a short step-by-step guide. For a more thorough introduction, please check the documentation within Tracer:

Help > Introduction > Quick Start

Creating a new PSF

For a detailed description of the simulation process:

Help > Setting Up and Running a Simulation

In Tracer:

1. File > New Simulation... (Ctrl-R)
2. Make your material stack (substrate, any intermediate layers, resist stack)
   • Get resist thickness either from:
     • Thickness measurement of your spun and baked resist, e.g. stylus profiler over a scratch
     • Estimate from technical data sheet

       e.g. PMMA A4 950K is approx. 2000 Å = 200 nm

   • Substrate thickness doesn't matter too much, but better be safe than sorry. Most common substrates at QDev are 500 um.

     Substrate thickness is crucial if you're exposing on membranes!

     In this case you might need two PSFs, one for membrane, one for full substrate stack.

3. Change beam energy and spot size
   • Calculate the beam FWHM using Shiv's Unofficial Dose Calculator

     e.g. 100 kV tool, 40 um aperture, 500 pA current gives a spot with FWHM of approx. 2.7375 nm

4. Don't make the number of electrons too small. 1 million is OK, more is better but takes time.
   • On Design 5 it's roughly 200 000 electrons per minute.
   • On Design 7 it's roughly 100 000 electrons per minute.
5. Don't make the update interval small, it takes away resources from simulation. 60 s is okay.
6. Right click the bolded simulation line > Z-Average 2D... > OK
7. Right click the averaged PSF > Export PSF...

   Save in your folder on Z drive

Importing the PSF to Beamer

In Beamer:

1. Double-click any PEC module
2. Click Archive
3. Click Import...
4. Select your file
5. Clear the tag or edit it to something concise like your name, or perhaps add extra information. E.g. the current for which you calculated the FWHM or a standard substrate name.
6. Click OK

Using the new PSF for PEC

In Beamer:

1. Double-click the PEC module
2. Click Archive
3. Select the desired PSF
4. Click OK
5. Done!

How to: predict base dose for a known process but a different substrate

If you want to use an existing resist process for a different substrate:

1. Simulate both known and unknown substrates with the same resist stack
2. Select representative PSFs to compare in the simulation list for each substrate
3. Right click > Dose Factor
4. Done!

   This will not be 100% accurate but will give you an idea for dose test values

Detailed background and instructions online.