GEM SEMI standard (Generic Model for Communications and Control of Manufacturing Equipment) or SEMI E-30 describes how a semiconductor equipment shall communicate with a MES (Manufacturing Execution System), usually called ‘Host’ in GEM standard.
GEM is based on other lower level standards such as SECS-II which defines the messages exchanged, SECS-I which defines communication by RS-232 or HSMS for communication via TCP/IP. For ease of reference, all these standards are often referred to as SECS/GEM or GEM/SECS.
In a typical use of GEM, the equipment signals to the Host its status changes such as the arrival of a cassette on a load port or the start of a process. These events are called Collection Events. They are usually associated with internal variables of the equipment: Status Variable or Data Variable. Status Variables are valid at any time, while Data Variable are only valid when the associated Collection Events are issued.
Events can be synchronous or asynchronous. Synchronous events are associated with the evolution of state machines representing the state of the equipment seen from the Host (Process State Machine for example). Asynchronous events are not linked to state machines transitions.
Equipment shall also signal to the Host alarms that occur.
These two basic functions (sending events and alarms) constitute the Online/Local mode for which the equipment is controlled locally by the operator via the HMI of the Equipment Controller software. In this mode, the equipment informs the Host of its status changes but does not start a remote process (no remote control).
In Online/Remote mode, the equipment receives commands from the Host to start a process or job: Remote Commands. In this mode the local operator interface is disabled. The equipment continues to send its status changes to the Host, which synchronize the Host with the equipment status to execute a complete scenario.
GEM also defines additional services that allow, for example, to download the list of recipes or process programs from/to the equipment or to ensure the regular sending of process variables to the Host (Trace Data Collection).
The SEMI E30 GEM standard is available from SEMI organization.
Agileo Automation SECS/GEM and PV2 software library implements GEM SEMI standard and facilitates its integration by providing a set of high level services and taking care of all the standard services that the equipment controller software does not need implement like Dynamic Event Report.
Implement SECS/GEM connectivity
When implementing SECS/GEM connectivity for a production machine it is necessary to define the specific interface of the particular machine . This specific model will be based on GEM. It will be materialized by a document specifying the machine interface, including the different sections required by the GEM standard. It will also include the definition of the GEM elements that are left free to the OEM such as the equipment description, the Process State Model and the exchanged variables. These latter have recently been grouped together in a SEDD (SEMI Equipement Data Dictionary) in XML format which includes in particular:
- Collection Events list
- Alarms list
- Status et Data Variables list
- Equipment Constants list
- Remote Commands list
After the implementation phase, which can be based on a off-the-shelf library such as the one Agileo Automation proposes, it is necessary to test this interface with a Host Simulator software that will allow SECS-II messages to be sent and received in place of the real Host to validate the proper functioning of the software and the machine before its commissioning into the factory.
Agileo Automation’s Speech Scenario tool allows these tests to be performed manually but also automatically to avoid regressions when the software is updated.
Specific Equipment Models (SEM)
For some equipment families, SEMI consortium has defined more specific models based on GEM, the SEM (Specific Equipment Model). We can mention the following:
- SEMI E88 – Specification for AMHS Storage SEM (Stocker SEM)
- SEMI E91 – Specification for Prober Specific Equipment Model (PSEM)
- SEMI E122 – Specification for Tester Equipment Specific Equipment Model (TSEM)
- SEMI E123 – Specification for Handler Equipment Specific Equipment Model (HSEM)
While these models do not fully define the equipment interface, they do provide a more limited framework for defining the equipment interface of the corresponding families (Stocker, Prober, etc.)
In addition, complementary standards are used to manage the robotic loading of the machines. These standards were developed at the same time as the 300mm diameter wafers were used and are therefore called GEM300, but it would be more correct to call them automation standards. For more details, see our introduction to GEM300 SEMI automation standards.
Need support getting started?
Agileo Automation has a team of experts with an average of 15 years of experience in SECS/GEM connectivity and having set up machines in the world’s largest fabs.
Do not hesitate to contact us to support you to:
- Specify the SECS/GEM interface of your machines (possibly in collaboration with your customers’ IT departments)
- Implement this interface and integrate it with it:
- your PC software by integrating our SECS/GEM driver as .NET library in C#, VB.Net, C++, Pascal Dephi
- your PLC via Modbus, OPC-DA or OPC-UA using our GEM4PLC architecture
- Validate this interface on your machines
- Support you in semiconductor production plants (fabs) for commissioning