by Vern Puchalski, on March 06, 2019
MES Models usually describe a simple UP/DOWN state for equipment. Real-world conditions require multi-dimensional states for individual lots/point-in-process-recipes. This article continues to describe a Process Capability system to model these conditions, vary these states and deploy complex run rules simply and easily for operations staff.
You’ve read about Process Capabilities on this thread and want to implement everything but need to know where to begin! Start small with static cases to demonstrate the concepts, help others understand how things are working, get integration into FAB systems working and prepare for the future.
The logical place to start is to do your IT-internal homework and prepare the most straight-forward cases for demonstration. You simply must start with a static (either never changes state or discretely changes state via a clear up/down action with saved history) so that you can prove that system enhancements in the Recipe Manager, Equipment Model and results in the Dispatch List are all correct and available for demonstration.
All that is really required is to return a list of zero to n Process Capabilities as parameters along with the Recipe Name at recipe selection time. This list of parameters will now be referred to as ‘Required Process Capabilities’. Creating this requirement will not yet affect the lot selection and run process.
You must find a way to create distinct UP and DOWN events in your equipment model that will change the Offered Process Capability state and log this state change in equipment history.
If required capabilities are found, then look for the associated named Offered Process Capabilities on the equipment. When Process Capabilities exist for the lot/equipment combination and the Offered Process Capability is either DOWN or not found on the equipment, mark the lot as Not Capable, show the missing Capabilities are the ‘Not Capable’ reason and block the operator from selecting the lot. Be very careful to ensure that everything is correct and production-ready at this step since it’s now possible for operators to see the effects of the Process Capability system.
While there are additional system updates that will eventually be required, the above will allow system demonstration and a FAB road show to build support for the idea.
Now that you have a demonstrable system, it’s time to create a few simple static examples. These must be real-world examples that are part of the daily FAB experience.
It’s now time to involve individual Process Engineers and find a few cases where they waste a lot of time ensuring the Production follows capability rules on individual equipment. This is best done one-on-one with Process Engineers and not in a group setting. You should specifically look for equipment sets that have one major control point and several unequal members. This may be a physical difference (e.g. EQ A can do High/Med/Low Res while EQ B can only do Med/Low Res product) or simple tooling or chemical changes (e.g. Resist Type changes, Target or Species changes). The idea is to find one ‘control’ item that you can clearly demonstrate across several pieces of equipment in the set when you move to the next phase.
Recipe-level Capability (aka ‘Recipe Verified’) is another demonstrable case but be careful to explain that turning individual Recipes on/off is control at an excessively detailed level. The system will run better if classes of recipes are turned on/off by a common Process Capability (chemical, quality function, technology, etc.).
Make sure you test and retest the associated systems to ensure bug-free operation. An obvious bug at this time can kill confidence in the system.
In your investigations, look for a Process Engineer who is willing act as a ‘champion’ of the new system.
Now is the time to demonstrate to Management and the broader Process Engineering audience the power of the system. Prepare a 5-minute presentation for the Morning Production Meeting (warn the FAB Manager what’s coming!) and present a system ‘teaser’. Schedule an hour in-depth system presentation and invite all interested parties. Make sure to name the Process Engineer(s) that helped you select the demonstration cases and invite them to express their interest publicly.
Once you have a few interested parties and have completed several demonstrations, select one or two (no more) simple test cases and release them in production. Make sure you announce all activity in the morning Production Meeting (should take no more than 30 seconds) and personally show Production Management the results as seen by the Operator. Let these initial deployments run for several months before proceeding to more advanced cases.
Get feedback directly from Process Engineers, Production Staff, etc. Track misprocess rate, etc. Attend the Morning Production Meeting and speak up at each misprocess, control or tool loading issue that could be addressed by future Process Capability enhancements.
This should get you started down the path of effective use of Process Capabilities. Please be aware that there are many enhancements possible to make the system more and more useful over time. These will be addressed in subsequent Process Capability blogs.
Written by Vern Puchalski
Vern joined SYSTEMA in 2007 with 20 years’ MES and automation experience in silicon wafer and chip manufacturing. He has been involved in numerous projects concentrating on automation-friendly MES implementations and extensions, dispatching, recipe managers and process-capability solutions.
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