How to Design a Process
When you work in TRL or ICL, you need to submit a process to the "process technology committee" (PTC) for review. This is a very simple step, and it helps to ensure that tools and other users' samples do not become cross-contaminated. This page walks you through how to design a process, and what to include in the process request.
If you are a not familiar with MTL, it can be difficult to choose the right tools and to know the "standard" steps to do even simple things.
Therefore, we strongly encourage you to contact other users or staff to get help drafting the first version of your process.
You may find that this will avoid much of the agony of choosing tools.
It also allows you to get critical insights into which parts of your process may be the most challenging to do, what to be aware of, and what results to expect from a tool.
Another very important reason for obtaining this feedback is that some tools are significantly more efficient (i.e. faster, cheaper, better results) than others.
As an example, depositing 1 um of Aluminum in the Endura will take just 15 minutes from load to unload, while it takes 4 hours to do the same in the eBeamAu.
But, not every process is allowed to run through the Endura as it is a Si CMOS-compatible tool.
For help getting a process together, you can email ptc@mtl.mit.edu to find someone to meet and discuss your project with. Ideally, include a short description of what you wish to accomplish.
Why does my process need to be reviewed?
When your process is reviewed, the PTC committee doesn't really evaluate whether your process makes sense, is practical, or will be successful.
Instead, the only concern is to ensure that your sample (as progresses through the process) will not accidentally contaminate the tools or other users' work.
For that same reason, samples from EML-tools are not permitted to enter any TRL or ICL tool.
Similarly, there is a distinction between "green" and "red" processes:
- "green" processes and tools are traditionally used for silicon transistors, where device performance can be damaged by even small quantities of contaminats: these include most metals (e.g. Au, Cu, ...), metal ions (e.g. K+ or Na+), or dopants.
- "red" processes can tolerate many of the above contaminants. But some restrictions still exist, to protect a tool's performance (e.g. lead-compounds can impair the performance of a dry etcher).
What should a process flow contain?
The process should specify:
- The starting material (e.g. 6" silicon wafers, GaAs pieces, Pyrex wafers), because some starting materials may inherently require "red" tools (e.g. GaAs and Pyrex). Also, you need to include any processing that was previously performed on these samples (e.g. 6" wafers that received a 0.5um thermal oxide from Company X).
- The sequence of tools that your sample will run through.
| What? | Why? |
|---|---|
| Lab (ICL/TRL/EBL/EML/Other) | To identify the physical location. |
| Coral Tool Name | The Coral tool name uniquely identifies a machine. For example, "PECVD" is not a tool name, and is ambiguous: it could be many tools (sts-CVD, DCVD, concep1, ...) |
| Any details as to what is being done | Many tools can deposit or etch a range of materials, and such details can be important in reviewing the process. Here you specify what material and thickness is deposited or etched, what photoresist spun on, etc. |
| Sample contamination state (e.g. "red" or "green") | Specifying this helps you plan which lab-ware and tweezers to use. |
| Any notes that can help explain the logic of the step carried out | This is mainly for your own benefit, but sometimes can help you get suggestions that make your process easier. |
Option: Build a Process Online
As you browse through the tools and their capabilities on this website, you can add tools to an ordered list to build your own process (or just remember the tools).
The design allows you to create a detailed process, and assist you by running a simple check of your process sequence against the PTC matrix.
- The tools are shown on the sidebar, and you can always review or modify the process.
- For common lithography steps, we have created the ability to automatically add a sequence of process steps with recipe descriptions.
- You can use an Excel template to export your process, which you can then modify, save, or print as PDF to submit in a well-formatted style.
- The website will help you flag steps where the PTC matrix may be violated, so you can modify the process and substitute in a suitable tool.
How do I submit a process?
Simple. You send an email to ptc@mtl.mit.edu, and attach your process. But put your process name into the email subject line (so we know what to call it and how to find it).
What is the timeline for process review?
Once you email your process to ptc@mtl.mit.edu, you may get immediate feedback if you have a blatant contamination problem.
The process will then be reviewed at the weekly PTC meeting (currently Friday at 11am, but check the recent PTC minutes sent to the mtl-all email list, for the actual weekday & time).
There are different outcomes:
| Response | Description |
|---|---|
| Process is approved | That's it, you're ready to go! |
| Process is approved, see (XYZ). | The process is good, but before starting please contact the PTC member named here, because there was some simple feedback or suggestion. |
| Process is under review, see (XYZ). | The process requires a revision or there are more detailed suggestions. You can email the PTC member named here to arrange a time to meet and discuss. |
If you have doubts about your process or how to fabricate your device, it is usually better (and ultimately faster) to seek out direct feedback first, instead of struggling and submitting an insufficient process. The page get process feedback has more information on how to do this.