SECSII

SECS II (SEMI Equipment Communications Standard II) is a component of the SEMI SECS family that specifies the data definitions used for exchanging information between manufacturing equipment and host systems in semiconductor fabrication. It defines the content, structure, and semantics of messages, including status information, alarms, events, process data, wafer and lot data, and control commands. The standard is data-centric: messages are built from data items defined in a binding data dictionary and organized into streams and functions (SxFy) that identify the message type.

SECS II does not prescribe how messages are transported; that role belongs to SECS-I or higher-layer transport services such as HSMS (High-Speed SECS Messaging Service) over TCP/IP. In practice, a host and equipment interchange SECS II payloads using one of these transports, enabling reliable, automated integration in fabs.

SECS II supports a range of message classes, including primary messages initiated by a host and secondary messages in response, as well as event and alarm reporting. It provides the building blocks that underlie the Generic Equipment Model (GEM), which standardizes how equipment should present data and respond to commands for interoperability.

The standard is published by SEMI and has been widely adopted across semiconductor manufacturing, with many vendors providing SECS II implementations or adapters. Effective use requires careful mapping of equipment data to SECS II items and rigorous testing to ensure interoperability.