Processing - How Do I…?

Below are answers to common processing questions in the NanoFab.

Lithography

Mask Plates - How do I order a mask plate?

• How to order a contact mask plate
• How to order a mask plate for the GCA Steppers
• How to order an ASML mask plate

Calibration - How do I determine the correct exposure Dose/Focus?

On tools that have motorized autofocus (steppers & direct-write litho tools), you often need to analyze both the Focus Offset & Exposure Dose simultaneously. (Remember that "Focus Offset" is an offset from the autofocus' "zero" position of the wafer surface.) These tools will have a function for shooting a "Focus Exposure Matrix/Array", or "FEM/FEA", which exposes a grid with Dose varying in one direction, and Focus varying in another - the following explains how to find the Process Window from your FEM:

• Lithography Calibration - Analyzing a Focus-Exposure Matrix

Deposition

Metal Deposition

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Dielectric/Insulator Deposition

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Etching

Dry (plasma) Etching

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Wet (chemical) Etching

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Materials

Material "Quality"

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Alloying metals

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Experiment Setup

Design of Experiments (DOE)

Design of Experiments is essentially a way to apply the Scientific Method (hypothesis → variables → measurements → conclusions) to determining a physical manufacturing process, by varying process parameters and measuring outcomes in a controlled manner, allowing you to figure out

(a) how each parameter affects the process,

(b) identify a process good enough for your needs,

(c) what the process window is for this process (ie. if parameters fluctuate randomly, will your process still work).

One way to organize your experiments and measurements is with a spreadsheet; here is an example Spreadsheet and associated SEM's for developing a dry etch:

2023-09 InP Vertical Etch DOE

Travelers (aka. RunCards, Process Followers, Work Instructions)

Travelers are a critical way to

(a) plan out your fabrication before you start,

(b) record what actually happened during a fabrication run, and

(c) allow you to copy and modify existing/previous processes (avoiding redeveloping steps).

In the example traveler linked here, the critical columns are

1. The steps to be performed
2. The details of the step (eg. "why" you are doing the step)
3. The Wafer tracking columns on the right where you record
   1. The initials and date to indicate the step was completed, and/or
   2. Notes on what you changed/didn't work etc.

Example Traveller 2018 (DJ Dual-gate)

Example Job Folder (for all processing documents)

Tracking your processes

We have recently set up an example of how the UCSB NanoFab organizes our own fabrication jobs:

I have an example Trello task tracking board, and corresponding Google Drive folder here, showing how we organize our 'fab jobs over the years. We use Shared Drives extensively at the NanoFab, one for each "group" (Equipment/Facilities/Fabrication groups).

Augmenting human communication and memory, using

• Trello for job tracking and weekly passdown
• Google Drive (linked in Trello) for data retention.

The gDrive folder also contains example Travelers/RunCards/Process Followers and DOE's etc., which I highly recommend writing before you start 'fab or experiments.

Examples of Trello + Google Drive for tracking fabrication jobs

Tracking to-do and completed tasks. Example Job Folder on Google Drive with in-process traveler, microscope/SEM images, testing results etc.

Example job card for a fabrication run.

Written by Demis D. John, 2024-10-22