The Evolving World of SECS/GEM

Corina Mullen Cimetrix Inc. Salt Lake City -- Semiconductor International, 7/1/2001

At a Glance
Can these well-established forms of tool communication handle needs of 300 mm fabs and the market demand for e-manufacturing?

Since the creation of SECS/GEM protocols, the industry has relied on these communication methods to connect tools to the fab. As the industry moves to 300 mm wafer production, these protocols become more important than ever. These forms of tool communication have served the industry well, but as the migration to 300 mm production begins, what changes will have to take place for these communication protocols to meet industry demands, new options in connectivity and global communication?

What is SECS/GEM?

When the industry refers to factory automation, or factory communication, the reference is to SEMI equipment communication standards (SECS) and generic model for communications and control of manufacturing equipment (GEM). SECS/GEM is a communication method based on Semiconductor Equipment and Materials International's (SEMI) communications standards, E4, E5, E30 and E37 that allows production equipment to communicate to a factory host. The equipment can report important events or alarms to the host, and the host can send remote commands or process programs to the equipment. SECS/GEM has been widely accepted across all levels of the semiconductor industry since its publication in 1992. The integration of GEM-compliant equipment into integrated circuit (IC) factories has saved billions of dollars by reducing misprocessed product. In addition, yield in those factories has increased because of improved data integrity. Manpower requirements have been decreased by reducing time spent by personnel entering data and processing programs.

The ultimate goal of fab automation is to eliminate the need for humans within the actual manufacturing facility. SECS and GEM have been basic steps to accomplishing this goal. The data-gathering and basic process control defined in the SECS/GEM standards have saved innumerable man-hours while improving yield and virtually eliminating misprocessing.

Limitations of SECS/GEM

As the industry moves to 300 mm wafers, SECS/GEM standards face limitations that prevent IC manufacturers from achieving this goal. The increased wafer size creates challenges in transporting wafer front opening unified pods (FOUPs) from tool to tool. Each of these FOUPs is filled 25-wafer and weighs approximately 40 lb, which is much heavier than the OSHA limit for repetitive lifting. To move these wafers through the manufacturing line, automated material handling systems (AMHS) are being perfected. The mechanics of these systems are deceptively simple. Wafer carriers are moved from storage location to processing location, transferred to the equipment, transferred back to the AMHS, and transferred from the processing location to storage location.

New 300 mm SEMI standards

Because of challenges facing 300 mm automation, it has become necessary to develop new SEMI standards. The 300 mm standards are the next step toward a fully automated fab. The first of these new standards allows IC factories to know the location of a given FOUP. E87, the standard for provisional specification for carrier management, provides methods by which carriers can be tracked throughout a manufacturing facility at all times. Along with the existence of AMHS, this standard allows carriers to be moved throughout the manufacturing facility without being touched by human hands.

The proliferation of computer chips in medical devices and the desire of retailers to ascertain responsibility in the case of catastrophic chip failures require the individual substrates to be tracked throughout a manufacturing facility. This prompted the creation of the second SEMI standard, E90 — specification for substrate tracking. It provides methods by which a substrate is tracked not only by the carrier in which it resides but by the equipment on which it has been processed and, depending on tool type, the chamber in which the substrate was processed.

With the increase in wafer size comes an increase in the number of die. With the possibility of more than 10,000 die per wafer and more than 250,000 die per 25-wafer carrier, it is probable that foundries serving specialized markets will have orders that will not require a 25-wafer run. There is a distinct possibility, however, that multiple orders may have identical requirements at batch processing steps with differences primarily at the single-wafer photolithography steps. Also, with the increase in the number of die per wafer, each wafer becomes significantly more valuable.

These conditions have necessitated an ability to designate recipes and recipe parameters on an individual wafer basis. This ability is provided by the third and fourth SEMI standards: E40, standard for processing management; and E94, provisional specification for control job management. These standards outline a method by which processing can be specified for an individual wafer instead of solely for a carrier of wafers, providing wafer-level flexibility and the capability to compensate for batch non-uniformities on a wafer-by-wafer basis.

The four previously mentioned standards — E87, E90, E40 and E94 — along with E39, the object services standard, are referred to as the 300 mm standards. These standards are based on the high-speed messaging service (HSMS)-SS transport protocol and the SECS-II message formatting, but go significantly beyond the requirements of GEM. While GEM provided a way for a host to monitor and control the working of each piece of production equipment, the 300 mm standards provide the groundwork for production equipment to provide information that is vital for the optimum utilization of other production equipment, such as film thickness measurements to be fed forward to calculate an individual substrate etch time or fed backward to adjust processing time on a furnace recipe (Fig. 1).

Current state of communication

2. To allow real-time process control and remote troubleshooting, equipment will require the ability to communicate with both multiple host applications and multiple subcomponents.

Currently, most of the management of equipment-to-equipment message transfer is via a factory host, usually in conjunction with a manufacturing execution system (MES). In the future, too much information will be transferred between machines to be passed through the MES. This deluge of information will need to be managed by a separate system, such as an advanced process control (APC) or advanced equipment control (AEC). Alternatively, this information could be transferred directly from equipment to equipment. In either case, the inability of a single host to accommodate all of the information needs of the manufacturing line will require that equipment be able to communicate with multiple host applications simultaneously (Fig. 2).

Most manufacturing equipment requires internal communication between third-party hardware and the machine control software. There are multiple ways to communicate between purchased subcomponents and the main equipment controller. Many suppliers of subcomponents support only proprietary communication methods. If it is necessary for an equipment manufacturer to support multiple suppliers for a single component, the equipment manufacturer is forced to provide multiple internal interfaces for communication to that component.

Since the information provided by each of the different incarnations of a single component will be similar, if not identical, the information transfer can be accomplished via a non-proprietary, generic interface based on a public protocol, such as SECS. By requiring that suppliers of subcomponents provide a SECS interface, original equipment manufacturers can change subcomponent suppliers without the need for major revisions of internal communication software.

The existence of the SEMI standards is not sufficient to provide communication from the equipment to the factory or within the equipment. The standards must be implemented via software. In the early days of GEM, many equipment manufacturers developed their own SECS/GEM software. The development of these proprietary SECS/GEM packages required up to 18 months of dedicated programmer effort at a cost of $250,000. The SEMI communication standards have been written so that much of the information to be provided by production equipment is generic. The common nature of the standards allowed the development of generic SECS/GEM software by third-party suppliers.

The advent of third-party software suppliers reduced the time required to implement SECS/GEM from approximately 18 months to four to six months. This reduced time to market and lowered the cost of providing a GEM interface from about $250,000 to an estimated $50,000. The use of third-party SECS/GEM software also provided an advantage to the IC fabs. Since any standard has areas open to interpretation, the quality and functionality of the proprietary SECS/ GEM interfaces was not consistent across manufacturers. However, with third-party software, the generic portions of the standards were provided yielding consistent interfaces across the industry.

As the industry moves to 300 mm, some equipment manufacturers are again choosing to create their own communication software. In addition to being exceedingly costly for the equipment manufacturers, these proprietary 300 mm SECS interfaces are not likely to provide the IC manufacturers with complete, consistent, timely communications. It has been estimated that the completion of a proprietary 300 mm SECS interface will require at least five man-years.

Certain 300 mm standards are still listed as provisional. Some of the standards have had functionality and services defined, but do not have the SECS messages to access those defined standards. As the standards evolve, an additional two to three man-years of effort will be required to determine and implement the changes and additions to the standards. This effort is in addition to the initial development effort. The development and sustaining of the 300 mm communication capability will require approximately seven man-years spread over the next three years. This yields a cost of more than $1M for each proprietary 300 mm equipment communication interface.

Third-party software suppliers have developed packages to provide support for SECS/GEM and the 300 mm communications standards. There are two leading suppliers of stand-alone 300 mm software for the semiconductor industry: Cimetrix and GW Associates (Sunnyvale, Calif.). Both suppliers provide equipment manufacturers with SECS/GEM software and software to implement carrier management, substrate tracking, process job, control job and object services.

The Cimetrix product, CIM300, is a modular, COM-based solution for the Windows NT/2000 operating systems. CIM300 has been designed to overlay implementations based on selected commercial SECS/GEM products. Equipment manufacturers are currently integrating Cimetrix CIM300 modules that support carrier management, substrate tracking, process job, control job and object services. The equipment manufacturers are expecting to ship full implementations of these 300 mm standards by late Q2 2001.

3. Modular architecture in third-party communication software allows equipment manufacturers to implement functionality as needed. This is important for manufacturers that have implemented partial solutions without the aid of third-party software.

Cimetrix also has modules in beta testing to support E58 ARAMS and E41 exception management. Also, Cimetrix markets a SECS/GEM solution, CIMConnect Pro, that provides a mechanism to communicate with multiple host applications and subcomponents. It also enables equipment manufacturers to create non-SECS/GEM drivers to support internal and external communication to applications that do not support the SEMI communication standards (Fig. 3).

The GW Associates product, GWconX300, is Windows NT software for implementing communications links on semiconductor wafer fabrication equipment. GWconX300 includes a SECS/GEM foundation, provides one SECS connection to the host and can support several SECS links to equipment subsystems. This product includes support for the SEMI standards E4, E5, E30, E37, E39, E40, E87, E90 and E94.¹

These software suppliers are providing communication software to the semiconductor industry that yields tangible financial rewards for the equipment manufacturer. By reducing the number of software developers required to implement and support SECS/GEM and the 300 mm standards, third-party communication software saves equipment manufacturers money. By reducing the time to market, third-party communication software accelerates the receipt of revenue.

The future of fab communication (e-manufacturing)

With the creation of 300 mm connectivity software, the ability to fully automate a fab is becoming a reality. The connectivity software is being engineered with the future of communications in mind. Each tool provides a vast amount of sensor data that may or may not be of normal interest to the factory. However, this information becomes invaluable when troubleshooting process or equipment problems. Many times equipment is down for hours or days while waiting for the correct maintenance person or field service engineer to arrive and verify the output of sensors or to perform a simple test.

One solution being discussed in the semiconductor industry is the Web enabling of certain equipment data and controls. This would allow service personnel in the building or halfway around the world to monitor sensor and process data or to perform certain tests and procedures. This idea is in its infancy, but is quickly maturing. Even in its early stages, it is apparent that two main issues will need to be addressed. The first issue is the ability for the equipment to communicate with multiple host applications simultaneously. Severe limitations in throughput will occur if all equipment data for all purposes is managed by the MES. The second issue is security. It is necessary to contemplate the possibility of unauthorized access halting or damaging a Web-enabled manufacturing line.

As communications methods and improved intelligent systems become available, the human requirement in the manufacturing facility can be further reduced. Integrating metrology equipment and using APC will reduce the engineering time used to determine correct subsequent processing. Integrating metrology equipment and using AEC will reduce the engineering time used to regulate process equipment.

Web-enabled equipment will allow for a large part of maintenance troubleshooting to be performed remotely. Certain maintenance functions can be performed remotely, reducing the number of maintenance personnel required to be physically in the facility. The remote capabilities will reduce both response time for field service engineers and the number of unnecessary site visits.

4. E-manufacturing streamlines production by reducing human monitoring and intervention in mundane tasks.

As more information is available from the manufacturing facility, the fab automation can be connected to commercial e-applications, creating an e-manufacturing facility. For example, a machine can be programmed to track the time or number of processed wafers allowed before a consumable, such as a filter, must be replaced. When the limit is reached, the machine can refuse additional processing, place itself in a down state on the MES, and contact the parts inventory management system. The parts inventory management system could then contact the supply management system, which would contact the supplier's consumable ordering system to place an order and have the consumable delivered to the customer. This scenario has been simplified, but it illustrates that a normal occurrence that would traditionally require seven human interventions could be performed completely via factory automation with virtually no opportunity for error (Fig. 4).

The chip industry is on the path to e-manufacturing. The initial foray into fab automation was SECS/GEM. After proving the benefits of factory automation and necessitated by the increase in wafer size, the 300 mm standards are now being implemented. In the next few years, SECS will be augmented by protocols that allow Web enabling of equipment. As these factory capabilities are coordinated with e-commerce capabilities, such as ERPs and supply chain management, e-manufacturing will emerge.

Corina Mullen, product manager for the semiconductor division of Cimetrix Inc., has more than 10 years of experience in the semiconductor industry, including academic research at Oregon State University. She has been instrumental in creating and sustaining host and tool-based communication software supporting SECS, GEM and the 300 mm standards for both GW Associates Inc. and Cimetrix.

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REFERENCES

1. See www.gwainc.com.
   

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