In the late 1980s and early 1990’s the Semiconductor Equipment Communication Standard (SECS) was starting to gain traction. Back then it was based on RS232 serial communication defined by the SEMI E4 SECS-I Standard. Later, SECS-I was replaced by the SEMI E37 HSMS standard. The content of the messages was defined by the SEMI E5 SECS-II standard. At the time, that was all that was defined. It was a bit like the Wild West with each equipment vendor implementing SECS-II messages as they saw fit.
While it was cool to be able to connect to process or metrology equipment and collect data, specify the process, and monitor alarms, it was a big task to develop factory systems that interface to the equipment because each SECS-II interface was unique. One of the first tasks required when developing an interface was to perform an equipment characterization to understand and document the details of the SECS messages used by each equipment. The characterization report became the guide for developing the factory side interface to that particular piece of equipment.
Semiconductor factories were buying hundreds of pieces of equipment for their factories, and though there were usually multiple pieces of the same equipment, there were still many unique equipment interfaces in each factory. The factories had to develop unique interfaces for all the equipment they wanted to automate. This issue was a bit like the tail wagging the dog.
To change things so that each equipment interface wasn’t completely unique, semiconductor factories worked with SEMI to better define how the communication between factory control systems and equipment should work in the factory. In 1992 SEMI published the first version of the E30 standard – Specification for the Generic Equipment Model for Communications and Control of Manufacturing Equipment (GEM). This standard provided a stable base for both factories and equipment manufacturers to work from in developing equipment interfaces. Message usage and contents were consistent, state models were defined, and interface capabilities were well-documented.
Since that time, other equipment communication standards have been developed and approved for use in semiconductor manufacturing. The GEM300 standards for factory automation (E39, E40, E87, E90, E94, E116, E148, and E157) have made it possible to enable fully automated manufacturing. The EDA standards (E120, E125, E132, E134, and E164) make it possible to implement consistent, well-defined data collection.
Even though the SEMI standards are quite well-defined, they are only as good as the implementation on the equipment. Compliance testing is essential for both equipment manufacturers and factories to ensure the interfaces are compliant to the standards and function as defined. In the early days of GEM, compliance testing was an essential piece of factory acceptance of the equipment. Initially, there wasn’t a lot of experience with developing or using the equipment interfaces. This meant that we needed some way to test compliance to ensure the interfaces worked as expected. Even though GEM and GEM300 are now quite established, compliance testing is still important to ensure the communication interfaces will support the functionality needed in the factories.
Compliance testing for the EDA standards hasn't been as well-defined as it has been for GEM and GEM300. In 2011 the International SEMATECH Manufacturing Initiative (ISMI) published the ISMI Equipment Data Acquisition (EDA) Evaluation Method document which provided step-by-step instructions for testing and evaluating an EDA interface. Using that document, Cimetrix developed EDATester which automates the instructions defined in the Evaluation Method document. This automation allows testing that would normally take several days to be done in a few hours, or less.
Having standard, well-defined communication interfaces for semiconductor manufacturing equipment is important to automated manufacturing and data collection. The ability to test developed interfaces and assure that they are compliant with the SEMI standards is essential to successfully introducing the equipment into a semiconductor factory.
Cimetrix compliance test tools automate the testing process making the acceptance process smooth.