The SECS/GEM Semiconductor Equipment Communication Standard/Generic Equipment Model interface was developed, maintained and published by SEMI Semiconductor Equipment and Materials International organization, a non-profit organization. In terms of formal standards, SEC/GEM can be called SEMI standard E30, but most times it is just referred to as SECS/GEM standard or the GEM standard. “It refers to the SEMI standard E30 which describes a generic model for equipment behavior and communication using a subset of the message types defined in the SEMI standard E5. Deployment of SECS/GEM interfaces will generally use TCP/IP networking as specified by SEMI Standards E37 and E37.1 but RS-232 serial connections can also be used as described by standard E4. The latter is more common for older equipment. The SEMI standards have shorthand names as well as their official identifiers, thus E4, E5, and E37 are also referred to as SECS-I, SECS-II, and HSMS respectively” [1]. Its main focus is to productive economically and financially for both equipment suppliers and device manufacturers “by defining 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” [2]. The SEC/GEM standard is a standard implementation of SECS-II standard.
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Generally, the standard helps to define scenarios and messages, it also allows factory software to be able to monitor and control equipments manufactured. Most of the equipments in photovoltaic, semiconductor, electronics assembly, flat panel display, surface mount technology and other manufacturing industries around the world enable communication between factory host software with the machines in order to monitor and/or control the machines, this is achieved by providing a GEM/SECS interface on the manufacturing equipments/machines. The standard can be applied to almost all equipments in the manufacturing industry because the standard was written with few semiconductor-specific features in it.
Introduction
SECS/GEM is a common adopted communication interface that depends in its modern form on strong TCP/IP internet networking. The SECS/GEM protocol enables an extensive automation which helps to avoid expensive mistakes and relieves humans of repetitive, deadly, tedious and error prone work, thereby making it be of high value in the Semiconductor and Electronics industries. The success stories of SECS/GEM are:
Establishment and verification of equipment setup before processing for automated systems.
Transfer of important data in Measurement tools without operator transcription
Enables handling systems to transfer materials and coordinate movement automatically
Enables equipments to be effectively optimized and monitored by providing alarms and reports for events.
The original SEC/GEM protocols reflect an engineering approach of directness and efficiency as they were developed by hands-on implementers, but as the scope expanded, inputs from many companies and many points of view started to surface. This lack of coherence in the original and subsequent standards made it seem like the SEC/GEM standard was something developed by several teams for a narrow set of requirements. When the whole SEC/GEM standards are considered in general, a lot of inconsistencies and imperfections are noticed although this doesn’t count when the value of products received is considered.
SECS/GEM Standard Usage in Industries
Semiconductor Front-End
The industry has been one of the major supporters of SECS/GEM and connected SEMI standards. The GEM300 standards which include the SEMI standards E116, E94, E40, E87, E90 and reference the E39 standard were defined by the semiconductor front-end industry and a GEM30 standard upon which the GEM interface is built is provided for each of these standards. In order to implement manufacturing automation in the semiconductor industry, on every 300mm wafer manufacturing tool, the SECS/GEM standard and an additional GEM 300 standards will be required.
Semiconductor Back-End
In the semiconductor back-end industry, a lot of equipment makes use of the SEC/GEM standard and some additional standards such as
Specific equipment model for testing-Semi E122 and
Specific equipment model for handler- Semi E123 standard.
Surface Mount Technology
In the surface mount technology industry, the SEC/GEM standard have been used for over 15 years, the SEC/GEM standard is important for inspection of equipments, placement of chip, pasting of solder est.
Photovoltaic
The SEC/GEM standard was only recently officially adopted in this industry as the “Guide for PV Equipment Communication Interfaces (PVECI)”. In previous years before its official adoption, lot photovoltaic equipment suppliers supported the standard. A new framework is defined by a fresh standard which makes use of the SEMI E148, SEMI E37 (HSMS) and other standards.
In an automated Semiconductor fabrication plant (a factory where devices such as integrated circuits are manufactured- commonly known as “FAB”), the SEC/GEM interface can begin and end processing of equipment, measure collected data, make changes to variables and recipes are selected for products in a specific way;
SECS/GEM Standards
SECS-I
SEMI Equipment Communications Standard 1 Message Transfer – this standard is used by SECS/GEM for communication between host and equipment as defined by RS-232. Due to speed limitations, the SEC-I standard is quickly fading and being replaced by the HSMS standard due to the following disadvantages;
Slow transmission rate of data over RS-232 using the SECS-I protocol.
Local area network (LAN) access not provided by the standard.
Low noise immunity of RS-232.
SECS-II
SEMI Equipment Communications Standard 2 Message Content- Most functionality and standards used in SEC/Gem standard is defined by the SEC-II standard. A definition for similar equipment communication capability and behavior is also made available by this standard, in the semiconductor industry; it is the standard for communication between equipment and host. A lot of GEM compliant systems are not SECS-II compliant.
In SECS-II standard, message types are defined which cover a broad range of functions which are defined for specific purpose or for general use. A range of function and stream values are also provided in SECS-II standard defined for custom use in situations when the predefined message types are not required. The Stream and Function together show what the message mean. SECS-II message types are categorized by Stream, e.g. Stream 1 is associated with equipment status events and Stream 6 is associated with equipment monitoring and other events.
A reply may be required for a sent message, an odd number is used to indicate an asynchronously or independently sent and this type of message is called Primary message. A reply message to a previously sent message is indicated with an even function value a number ahead of its corresponding primary message function value and it is called a Secondary message. In order to send multiple messages without waiting for each reply before sending another message, a unique 4byte integer message header is used to associate a secondary and primary reply message; this unique integer is set by the sender.
HSMS
SEMI standard High Speed Message Service-Single Session- the HSMS is now used in place of the SEC-I standard by SECS/GEM for communication between host and equipment defined using TCP/IP network communication. A point to point protocol for communication is defined for the communication which allows only one client to one host to use a specific port at a particular time. It possesses the following advantages;
It provides higher speed alternative to the SECS-I protocol
Low cost
High reliability and
Wide platform choices
GEM
The GEM or SEC/GEM standard specifies how specific tasks, such as reporting events, collection of data and management of recipe of equipments are carried out using SECS-II messages while communicating with the host.
All semiconductor manufacturing tools need to follow the SEMI SECS/GEM standards to interface with the equipment manager and MES (Manufacturing Execution System -Allows one or multiple equipment GEM interfaces to communicate at the same time with a host system). These standards include the semiconductor equipment communication standard SECS-I or SECS-II, high-speed SECS message services HSMS, and generic equipment model (GEM), etc.
Furthermore, to take full advantage of CIM Framework (Computer Integration Manufacturing-The CIM Framework defines a framework of components that provide the functionality common across CIM applications and enables integration of those applications.), SEMI developed an object-based equipment model (OBEM) standard so that the equipment can communicate with the CIM Framework directly by method invocation without using the SECS/GEM protocol. The OBEM standard focuses mainly on providing definitions, services, and behavior of physical and logical objects of which equipment is typically composed.
To communicate with GEM capable host, GEM equipments can communicate using one or both of the protocols listed below;
TCP/IP (using the HSMS standard, SEMI E37)
RS-232 based protocol (using the SECS-I standard, SEMI E4).
Monitoring and controlling equipments with a GEM interface with the aid of SECS-II messages can take minutes (or even seconds) in order to make a connection for communication, this is specified by GEM. Monitoring the machine’s activity for factory GEM host software provides the following benefits for equipment manufacturers.
Improving of the machine’s quality can be allocated more time and money by providing a common interface to all factories.
Processes and production can be improved by allocating more time and money to them, rather than setting up communication to the machines.
The SECS/GEM Conceptual Model
Below are descriptions of SEC/GEM message exchanges in conceptual mode as seen in the equipments.
Variables: Three different categories of variables are identified in SEC/Gem protocol. The first category of variables are Status Variables, they are read-only values which serve as communication channels, for example readings from sensors or value of clock to the host, they can also be used to describe equipments for Example list of the collected data events which at that moment are enabled for reporting. The second category is Data Value Variables and they are similar to Status Variables in the sense that both of them are read-only data items and the values which they hold can be passed to the host. The difference between the first category- Status Variables and the second category- Data Value Variables is that a it may sometimes hold an invalid value. The last category of variables is the Equipment Constant Value variables, they are not constant variables, they can be changed by the host to limited values specified by the equipment which are then communicated in a particular message format e.g. collected data or reported events.
Event Reporting
This type of message allows passage of an event to be notified to the host by the equipment to e.g. status change or process completion. A previously defined event report which contains a fixed set of variable values was provided for older equipments while modern equipments provided support for dynamic event report which allows configuration of data item variables which are included in the set during communication of an event report by the host. The whole method is powerful and general. E.g., after downloading a progress program, it can be used to communicate result validation for a program as an asynchronous event. A detailed description is provided in the GEM standard of the most commonly reported events which show changes in process state and changes in control state.
Alarm Reporting
An alarm is not an event in that it shows an unwanted condition with two states; a clear and set state. E.g., an alarm clear condition message could be sent as alarm set for a compressed air input which requires an alarm if the air pressure input extends below the needed amount process tool that it relies on and if later the air pressure was restored an alarm clear message could be sent. Reports of alarm set and alarm clear conditions are required as collected data events in SEC/GEM. The ability to allow same dynamic event report technique and software logic technique to set conditions of alarm and data context by the host makes this feature more desirable.
Control State Model
A specification of control state model that makes sense for making use of both automation and operator actions in a safe way provided for SEC/GEM interface. Remote control of the equipment cannot be assumed by the host except it is allowed at the equipment. In common conditions e.g. maintenance performance or qualification of process activity with the host communication being ignored, the concept of the SECS/GEM interface provided is either off-line or on-line.
Remote Commands
Remote Commands can be sent by the host on equipments to control equipment actions such as processing in the SECS/GEM interface. There is similarity between a Remote Command and a programming procedure call in the sense that it is possible to pass arguments of data items as values for an indicated action. E.g. Execution of a specific process program. Remote Commands have the needed flexibility to allow automated factory equipments to be able to carry out various actions which are provided on the user interface tool by using the SECS/GEM. This feature is greatly appreciated by many factory users as it saves them time and money.
Trace Reporting
This feature provides reports on chosen variable values from time to time, although the ability to use the trace reporting feature for detecting accurate endpoint is lacking but there is often a higher expectation of its value than is necessary since it can support a remarkable demonstration. Some of the reasons why these features are lacking within the equipment system include; instrument intelligence, computer proliferation and controllers of software processes. It is wrong to assume that one controlling program running on a computer will have coordinated and instant access to all relevant information required. There is need for good planning for time precision of compiled data between many sensor readings and management in regards to process initiation for the data collected, all this information will have to be generated from the start and put into the control system in order to have an accurate and precise report.
Terminal Services
This feature is important in order to support acknowledgment of short text messages and display message types, it has less use in production area but it has support for demonstrations and example programs. Most factories that are using SECS/GEM interface and have made investments in automation are doing their best to step away from production scenarios that depend on operator acknowledgment and displayed messages. Even in the usual factories where all equipments are using similar languages, there is high tendency that the navigation button for the menu to be able to see and approve terminal messages will be different for different types of production tools. Therefore deployment of operator station software by the factory is encouraged if operator interaction is needed instead of deployment by each equipment vendor.
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Connection in SECS/GEM Protocol
Communication between the equipment and the host is defined using a single connection. The SECS-I standard makes use of RS-232 serial ports for connection, while the HSMS makes use of TCP/IP for connection. Mostly, a single is provided by the equipment to be used by one host alone. In SECS/GEM standard message types can be defined for host use alone, for equipment and for both sides. Equipment can connect to several parts of other equipments to function as a host and this is an efficient method of bringing several parts of equipments together in a fabrication cell. However in HSMS, there is usually independent connection for several parts of equipment. SECS/GEM also allow each device identification to have a modulated message when sharing a connection but this is usually found on systems with older RS-322 versions and not advisable to be used on new deployments. Messages can be exchanged between host and equipment once a connection is established between the two of them and the connection can last for a very long time, in some cases connections are not cut except it is interrupted.
Communication in SECS/GEM Protocol
Generally in the implementation of SECS/GEM protocol communication, there are two parties involved; the equipment and the host.
In order to run GEM interface software on its computers, any equipment must comply and implement the SEMI standards. Establishment of communication on interface of SECS/GEM equipments is done by the manufacturer (factory) which runs GEM host software.
A host also referred to as line manager or station controller is a division or member of the Manufacturing Execution System (MES) of the factory. A direct communication can be set up by the host system on a single or among many GEM interfaces equipment at the same time using SEMI E37.1 HSMS-SS standard (TCP/IP based network communication) or SEMI E4 SECS-I standard (RS-232 based serial communication) Although in most modern factories, the HSMS-SS standard is widely adopted because of its convenience in such industries. Implementation of host-side communication must be allowed for the host to be able to use the SECS/Gem interface but it is not necessary for the host to comply with the SEC/Gem standards, since the standard is only required for the expectation of the equipment. To determine identity of software/ equipment, an online recognition system is put in place to be able to verify the identity of equipments.
Communication in SECS/GEM protocol is platform independent i.e. it can make use of various programming languages or operating system and it is done via a serial cable connection or a network connection. For exchange of data, a connection on the host side is usually set up on a computer system which is made available by the factory and connection on the equipment side is usually through computer controller which is provided by the manufacturer of the equipment
Control in SECS/GEM Protocol
In order to define the level of collaboration between the equipment operator and the host, a control state model is defined for the SECS/GEM standard. To control the equipment processing, commands like EXIT, BEGIN and RETURN can be defined for remote control to allow the host send commands. Many commands can be defined for equipments with their specific behavior when called.
The static feature of equipments enables setting equipment constant, retrieving equipment constant and equipment’s behavior to be monitored by the host. Equipment static configuration is required for SECS/GEM state machines. More equipment static variables can be configured by the host in terms of the behavior of the equipments.
Operation Notification in SECS/GEM Protocol
In order to monitor specific equipments operation, alarms on the Equipment collection need to be set by the host, this provides notification on significant, abnormal activities/events and even when dangerous events are detected and taken care of. A notification is sent to the host by the equipment for events that have been enabled for notification alone; any event not enabled for notification will not be able to send a notification to the host. In order to send the notification and also to reduce network traffic, a SECS-II messages format/standard is used to send the notification. Also to monitor certain activities by the equipment the host can define additional events which are needed by the SEC/GEM standard.
Data Gathering in SECS/GEM Protocol
Six different methods of data collection are defined by SECS/GEM. Here, there is a fixed way of data gathering where ability to gather information from the host by equipment is not enabled but the ability to gather information by the host from the equipment is allowed. The six methods are described below;
Request of status variable values which can be done at any time.
Request of equipment constant values which can be done at any time.
Request of report which contains the variables of collected data, constant equipment values and the variable status which can be done at any time.
Transmission of Messages. The report data together with a collection of events can be transmitted at the same time if the host defines the reports in the same SECS-II message; this reduces the obligation of the host during information poll because the feature allows data related to each event to be sent to the host to become available.
Poll status of equipment. Equipment from time to time/ frequently transmits the status variable values defined by the host at a set interval, which allows the equipment status to be polled by the host at each interval with no need for permission.
Configuration of limits monitoring. This enables a notification to be sent to the host by the equipment whenever a specified variable value moves across a host-defined boundary, with this there will be no need for the host to poll dangerous values. A definition of many limit boundaries can also be made.
Process Program (Recipe) Management in SECS/GEM Protocol
A process program “is the set of instructions, settings, and parameters under control of the equipment that determine the processing environment seen by the manufactured object (SEMI E30, 4.2.6.1)” [3]. The features of the Process program management include the following:
Downloading of process program to the equipment by host for storage on the equipment.
Query of process program for storage by host from the equipment.
Deleting of process program on the equipment by host.
Request of available process programs by host.
Sending of process program to the host by equipment operator.
Request of process program from the host by the equipment operator.
Selection of process program for execution by host using a remote command PP-SELECT
Notification of host by equipment operator on creation, edit, deletion and selection of process program on equipment.
Spooling in SECS/GEM Protocol
This allows information intended for the equipment to queue during break in communication or communication failure; the queued data can be purged by the host when communication is restored. Configuration of queued information is done by the host including the queue size, queue information and recovery of queue information and switching of spooling features on or off.
When considering the performance of old and new SECS/GEM standards, the new standard allows the setup of collected data with specification of the message rate in milliseconds by the host. Little network bandwidth can be used to transfer a lot of data in the SECS-II and HSMS standard because their message format is very efficient. There are many factors that affect the actual data rates such as SEC/GEM software in the host and equipment systems, network, and the hardware for the computer. In terms of performance, there was a limitation of 1 Hz trace for collected data in previous versions of the SECS/GEM standard.
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