SECS/GEM Data Items

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-SECS/GEM Data Items-
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• SECS/GEM is an industry standard, that defines
  standard process of communication between
  equipment and fab host software for controlling
  and monitoring purposes. By connecting SECS/GEM
  equipment, fabs can immediately gain operational
  benefits. Factory hosts can collect data in
  multiple ways. Along with event reports, the fab
  host often requires to poll the equipment for
  current data values. The host can directly
  request Data values , or can be sampled
  periodically in a trace report this process is
  called Data Polling.

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• There are 3 categories of Data Items defined in
  SECS/GEM standards-

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• Status Variables (SV)-
• Status variables are data items that identify the
  status of the equipment, or any of its
  components, such as sensors, meters, etc.
  Examples of status variables for process
  equipment are Temperature, Pressure, Gas Flows,
  RF Forward Power, Spin Speed, etc. These data
  items are generally not attached to events such
  as lot start, wafer start, etc. A factory host
  can query the status variables to the equipment
  any time or can define trace data setup through
  which it asks the equipment of supplying status
  variables at regular intervals. A factory host
  cannot change status variables of the equipment.

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• Data Value Variables (DV)-
• Data value variables are data items that are
  related to a certain event, such as lot start,
  alarm/error occurring on the equipment, wafer
  processing/measurement complete, etc. Examples of
  data value variables are Lot ID, Slot Number,
  Current Recipe, etc. These variables change only
  when a certain event occurs, such as selecting a
  recipe, starting lot processing, etc. A factory
  host queries Data Value variables through
  defining reports and associating the reports to
  events.
• Unlike status variables, data value variables may
  not have a value. For example, one of the data
  value variable is Alarm ID, which designates the
  ID of the most recent alarm. However, it can be
  empty if there havent been any alarms since the
  equipment was turned ON. A factory host cannot
  change the data variables of the equipment.

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• Equipment Constants (EC)-
• Equipment constants are data items related to the
  configuration of the equipment they could
  contain items related to the equipment hardware,
  software or SECS/GEM software. Unlike status
  variables and data value variables, a factory
  host can change equipment constants through SECS
  messages. Examples of equipment constants are
  Pump Down Time Limit, Equipment Standby Time,
  Pins Up Wait, etc.

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• Data Properties
• The Data types listed above have similar
  properties so that its convenient to define the
  data. The equipment supplier is required to
  provide these properties in a SECS/GEM manual so
  that the fab host will be able to understand and
  communicate with the data. Below are some of the
  important data properties of the Data Types

• ID Its a numeric ID that must be unique in the
  SECS/GEM interface. These IDs can be grouped by
  data type and are referred to as SVIDs (Status
  Variable IDs), DVIDs (Data Variable IDs) and
  ECIDs (Collection Event IDs).
• Name Its a name assigned to a data item so
  that we can identify it easily.
• Format Data type of the item.

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• Data formats can be simple (numeric, ASCII,
  Boolean) or complex (arrays, lists, structures).
  For example, numeric types can be I1, I2, I4, I8
  (signed integer types of different byte length),
  U1, U2, U4, U8 (unsigned integer types) and F4 or
  F8 (floating point types).
• Array types and List contain multiple values in
  the data item. For example, image data will be
  formatted as a Byte Array.
• Structure types contain a specific type of data.
  For example, a variable may represent a slot map
  which contains carrier information and also list
  of slots with their wafer placement status.
• Value Its the actual value of the data item.
  Data values are in an accurate, efficient,
  selfdescribing binary format so that its easy for
  the host to interpret the data. The data format
  allows collection of more data and with more
  efficiency.
• Alarms Collection Events (CE) also have IDs and
  names for their identification.

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Data Polling- The fab host often gets data on a
regular intervals through event reports trace
reports and that it defines. SECS/GEM also
provides a system for the fab host to poll data
based on its needs. www.einnosys.com
info_at_einnosys.com