A comprehensive reference guide to the SEMI SECS/GEM and GEM300 standards — the foundation of equipment-to-host communication in semiconductor manufacturing.
GEM (Generic Equipment Model) is a standard implementation of the SECS-II standard (SEMI E5). Most equipment in semiconductor, surface mount technology, electronics assembly, photovoltaic, LED, flat panel display, and other manufacturing industries provide a SECS/GEM interface so that factory host software can communicate with the equipment for monitoring and controlling purposes.
Because the GEM standard was written with very few semiconductor-specific features, it can be applied to virtually any manufacturing equipment in any industry. All GEM-compliant equipment share a consistent interface and certain consistent behavior.
GEM equipment can communicate with a host using TCP/IP (HSMS standard, SEMI E37) or RS-232 serial protocol (SECS-I standard, SEMI E4).
High-Speed Message Service — TCP/IP based network communication. Used almost exclusively in modern factories. Maximum message size of approximately 4.3 GB. More convenient and better aligned with modern manufacturing environments.
RS-232 based serial communication. The legacy protocol that has been largely phased out due to inherent speed limitations. Maximum message size of approximately 8 MB. Replaced by HSMS in most modern installations.
Once communication is established, the host and equipment exchange SECS-II messages. Each message is identified by a stream number (0–255) and function number (0–255). An odd-numbered function is a primary message; the consecutive even-numbered function is its secondary reply. Messages are sent as structured binary data to maximize content while minimizing bandwidth.
The GEM standard defines a comprehensive set of features for equipment-to-host interaction. Here are the key capabilities.
Key SEMI standards that form the SECS/GEM and GEM300 communication framework.
| Standard | Name | Description |
|---|---|---|
| SEMI E4 | SECS-I | RS-232 serial communication protocol for host/equipment communication (legacy, replaced by HSMS). |
| SEMI E5 | SECS-II | Defines the message content, format, and structure for all GEM communication. The foundation of SECS/GEM. |
| SEMI E30 | GEM | Generic Equipment Model — the standard implementation of SECS-II that defines equipment behavior and features. |
| SEMI E37 | HSMS | High-Speed Message Service — TCP/IP network communication, the modern replacement for SECS-I. |
| SEMI E39 | Object Services | Provides standard object management services referenced by GEM300 standards. |
| SEMI E40 | Process Job Management | Manages processing jobs on equipment — part of the GEM300 standard suite. |
| SEMI E87 | Carrier Management | Carrier tracking and management for 300mm equipment. Core GEM300 standard. |
| SEMI E90 | Substrate Tracking | Tracks individual substrates (wafers) through processing. Core GEM300 standard. |
| SEMI E94 | Control Job Management | High-level control jobs that manage process job execution. Core GEM300 standard. |
| SEMI E116 | Equipment Performance Tracking | Tracks and reports equipment performance metrics. Core GEM300 standard. |
| SEMI E148 | Time Sync | Time synchronization between host and equipment, referenced by GEM300 and PV2. |
| SEMI E10 | OEE | Overall Equipment Effectiveness — standard for measuring and reporting equipment performance. |
Key terms and concepts used in SECS/GEM implementations.
An abnormal situation on the equipment that may endanger people, equipment, or material. GEM allows the host to be notified when alarm conditions are detected and cleared.
A detectable occurrence significant to the equipment and host. GEM allows the host to be notified when events occur, enabling detailed activity tracking.
Parameters that can be sampled in time (e.g., temperature, quantity of consumable). Status values always contain valid information and can be requested by the host.
Values that may only be valid upon the occurrence of a particular event. Provides information specifically related to the event context.
Settings that are adjustable by the host. Used to configure GEM state machines and control various aspects of equipment behavior.
The set of instructions, settings, and parameters that determine the processing environment seen by the manufactured object.
A set of variables predefined by the equipment or defined by the host. Used to gather status variable, data variable, and equipment constant values.
High-Speed Message Service Single Session — TCP/IP network communication standard. Only one host client can use a specific port at a time. Has effectively replaced SECS-I.
GEM compliance is self-proclaimed — there is no official certification. Equipment must include a GEM compliance statement documenting which features are implemented.
Our team of SECS/GEM experts can help you build compliant equipment interfaces or connect your factory floor.