Wednesday, 16 January 2019

Introduction to SECS/GEM - Beginner's Guide - Introduction to SEMI E30 GEM standard

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Introduction to SECS/GEM - Beginner's Guide
SEMI E30 GEM standard
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SEMI E30 GEM Standard

The GEM standard defines a common set of equipment behavior and communications capabilities that provide the functionality and flexibility to support the manufacturing automation programs of semiconductor device manufacturers. Equipment suppliers may provide additional SECS-II functionality not included in GEM as long as the additional functionality does not conflict with any of the behavior or capabilities defined in GEM. Such additions may include SECS-II messages, collection events, alarms, remote command codes, processing states, variable data items (data values, status values or equipment constants), or other functionality that is unique to a class (etchers, steppers, etc.) or specific instance of equipment.


The COMMUNICATION state model defines the behavior of the equipment in relation to the existence or absence of a communication link with the host. It also defines how communication is established or re-established with S1F13/S1F14 when communication is broken


The CONTROL state model defines the level of cooperation between the host and equipment. The CONTROL model provides the host with three basic levels of host control which determine the host's ability to control the equipment:

  • OFFLINE (Lowest Level): Operation of the equipment is performed manually by the operator at the operator console. Equipment will respond with an SxF0 to any primary message from the host other than S1F13 or S1F17.
  • ONLINE/LOCAL (Middle Level): In this state, the host is only allowed to perform "read-only" operation like data collection. The host shall be prohibited from modifying any equipment constants that affect processes, remote commands that cause physical movement or which initiate processing.
  • ONLINE/REMOTE (Highest Level): In this state, the host may operate the equipment to the full extent available through the communications interface ("read-write" operations).


The PROCESSING state model is highly dependent on the equipment process, technology, and style. However, there are expected to be common aspects to these models.

Remote Command

Host can send command to instruct the equipment to perform an automatic operation. E.g.: START, STOP, PAUSE, etc. This is similar to the manual operation performed by operator on the console.


The GEM standard defines three types of variable which are accessible by the Host:

  • Status Variable: This is a "readonly" global variable defined in the equipment. Whenever there is a processing the equipment will update the respective status variable to reflect the latest data. E.g.: incremental of some counter, current/previous state, etc.
  • Equipment Constant: This is a "read-write" global variable defined in the equipment. Host can set or modify the equipment constant variable which may affect the setting that in turn change the way equipment's behaviors.
  • Data Variable: This is a "local" variable which only exists in collection event.

Data Collection

SECS/GEM a couple of avenues for Host to collect data or information from the equipment:

  • A set of status variable values can be requested at anytime using S1F3 command.
  • A set of equipment constant values can be requested at anytime using S2F13
  • Host can define report containing status variable, equipment constants and data variable then attaching it to a collection event. When equipment raise the event (using S6F11 command), the report containing those variable's values will be sent together.
  • Host can define traces which will do sampling of status variable data at a periodic basis.
  • Another way is leverage on alarm notification to collect more data with collection event. By standard, whenever an occurrence or clearance of an alarm, an event (collection event) must be sent to Host.

Alarm Notification

This feature allows the Equipment to notify Host for every occurrence or clearance of an alarm/error on the equipment. Alarm refers to those occurrence that are abnormal, undesirable and endanger people, equipment or physical material being processed.

Below are some of the characteristics of Alarm Management defined by GEM:

  • Each alarm has two associated state model. ALARM SET (occurrence) and ALARM CLEAR (clearance)
  • Each AlarmSet and AlarmClear has an associated Collection Event. This is to address the host's potential need for more extensive and flexible data reporting.
  • Host can requests which Alarms to be enabled/disabled and Equipment will only notify the Host for the enabled Alarms.


The SECS/GEM standard requires that each equipment provide a GEM Interface Reference Manual. It must include GEM Compliance statement, Complete SECS-II message documentation, State Model, list of status variables, equipment constants, data variables, alarms, collection events, etc that are defined/supported by the equipment.

And Many More...

Please refer to the complete standard for other features like: Spooling, Process Program, Terminal Services and Limit Monitoring.