…or how to move away from “just in case” data collection...
It’s a common process engineering request of the manufacturing IT folks: “Please collect as much data as you can during this process, and we’ll figure out what’s important later.” And this approach has worked fairly well up to this point. However, with 10nm (and below) production on the horizon, coupled with the desire to sample key parameters at ever-increasing rates, the amount of on-line data storage required to support this approach could skyrocket… to say nothing of the difficulty in sifting through all that data to extract the real information you wanted in the first place.
Fortunately, you don’t have to look very far into the SEMI EDA (Equipment Data Acquisition) standards (also known as “Interface A”) to find an excellent solution alternative. The portion of the standard equipment metadata model (specified by SEMI E164 – EDA Common Metadata) that deals with process execution (SEMI E157 – Process Execution Tracking) combined with the conditional triggering features of Trace Requests (SEMI E134 – Data Collection Management) enables a process engineer to precisely collect the right data at the right time at the right frequency without over-burdening the equipment or factory systems by collecting and storing less important data at the highest rates.
Let’s look at an example. The key state machine called for in the E157 standard (see figure below*) has 2 major states (NOT EXECUTING and EXECUTING) with intuitive transition events defined between them (Execution Started, Execution Completed, and Execution Failed). If you only care about tracking the overall execution time of the process recipes on a given tool, then a single DCP (Data Collection Plan) with a pair of Event Requests on the Started and Completed events is all you need. The difference in the timestamps of the corresponding Event Reports provides the necessary information.
However, if you want to monitor a baseline set of equipment performance parameters at a low frequency (say, 1 Hz) throughout the recipe, and collect the key parameters for analyzing process behavior at a higher frequency (50 Hz) during the most critical process steps (5 through 8), you would use a DCP with multiple Trace Requests triggered by the Step Started and Step Completed transition events between the two sub-states (GENERAL EXECUTION and STEP ACTIVE) of the EXECUTING state. Furthermore, you would use the conditional triggering feature of the Freeze II version of the EDA standards (SEMI E134-0710 or later) to produce Trace Reports only during the critical process steps. The figure below is one visualization* of such a DCP.
You may have noticed from this example that multiple triggering conditions are ANDed together to determine whether or not to collect the data and generate a Trace Report. But how do you handle the situation in which OR functionality is needed to produce the desired result, for example, in the case that multiple sets of recipe steps are considered critical (say, steps 5-8 and steps 11-13)?
This is where you can use one of the “tricks of the trade.” Simply define multiple Trace Requests with different sets of ANDed conditions to cover the range of ORed situations. For the case above, you would need two Trace Requests: one for each critical set of contiguous recipe steps (see visualization below).
Note finally that you can also apply comparison operators to analog values to trigger Trace Requests, which may be especially useful to sample specific parameters when some value crosses an important threshold.
Taken together, these techniques are sometimes called “data framing,” which is an important tool in the controlling the scope of factory data explosion that will soon be upon us.
This article is the third in our Models in Smart Manufacturing series – be sure to watch for subsequent postings that will expand on this theme.
We look forward to your feedback and to sharing the Smart Manufacturing journey with you.
*The visualizations of equipment metadata model fragments and DCP contents are those produced by the Cimetrix ECCE Plus product (EDA Client Connection Emulator).