Automation Needs Reach New Levels
Karl Gartland, Ed Sherwood IBM Microelectronics, Burlington, Vt. -- Semiconductor International, 7/1/2000
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At a Glance | | |
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Semiconductor fabrication has been and will be increasingly automated. Both economic and technical factors make automation necessary. The economic factors are summarized in the International Technical Roadmap for Semiconductors, which states: "Cost per function has decreased at an average rate of about 25-30%/year/function."1 This cost trend is reached through line size reduction, improved productivity via process improvements and yield gains, and wafer size increases. The technical factors result from the drive for line size reduction and yield gains, which are methods of reducing the cost/function.
Ever-decreasing line sizes create the need for increased process control, including run-to-run control, real- or near-real-time fault detection, and feedforward/feedback loops. This increased process control requires much higher levels of automation in the communication processing, and handling of data and information. Improved productivity has been driving increases in automated material delivery for several years. Automation standards are encompassing the following aspects of semiconductor fabrication:
Material transport and storage.
Material handling at the equipment.
Material tracking.
Dispatching and scheduling.
Equipment processing, process control and recipe management.
200 mm status
The first 200 mm lines, built in the late 1980s, had limited or no automation. Over time, automation was added to existing fabs and included in the design of new fabs. This diversity has resulted in many single-point solutions.
In the area of material transport and storage, most 200 mm semiconductor fabricators use automated systems to deliver wafer carriers from one stocker to another. A few progressive IC makers have developed and installed systems that deliver directly to equipment. Durables such as reticles typically are handled manually.
Material handling at the equipment is automated for most existing semiconductor equipment once the carrier is placed at a load port. Each equipment supplier has developed creative point solutions that enable the wide variety of demands placed on them by their diverse IC maker customers. As a result, the behavior and ensuing communication to the factory systems have created a complicated and resource-intensive integration effort for IC makers.
Material tracking, dispatching, and scheduling rely on people and data collection software for input, then utilize factory systems for decision support. However, most often an operator makes the final decision on what to do next.
Equipment processing and process control, as well as recipe management, have been automated partially in 200 mm fabs. Inconsistent behavior and equipment interfaces have prohibited complete automation of these functional areas.
300 mm opportunity
The transition to larger wafers is required for the industry to stay on the historic cost curve.1 There are unique or new requirements for automation in 300 mm fabrication. A 300 mm carrier loaded with wafers becomes too heavy for repeated manual lifting. This will require automated delivery directly to the equipment. Some IC makers have been doing this for some time, and the flat-panel display industry also has used automated delivery; but in 300 mm semiconductor fabrication this capability will be virtually absolute within the fab.
IC makers recognize that the requirements for increased automation also have increased the requirements for standardization. The cost of integrating hundreds of tools into the factory both physically and logically is reduced if each type and brand of equipment offers the same interface.
IC makers around the globe have worked together to define the requirements needed to implement a fully automated material transport and storage system. Industry competitors have come together in an unprecedented fashion to reduce the cost of the transition by defining as many common requirements as possible. These requirements are documented in the Global Joint Guidelines2, CIM Global Joint Guidelines for 300 mm Semiconductor Guidelines3 and the I300I Factory Guidelines4. These guidelines led to the development of SEMI standards. These standards enable an integrated automated factory.
Material transport and storage
New semiconductor fabs, particularly 300 mm, will rely heavily on automated material transport and storage. The Global Joint Guidelines for 300 mm Semiconductor Factories detail the requirements.
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 |  2. Standards for loadports enable the use of FOUPs delivered by overhead or floor-based transport vehicles. (Source: Asyst) |
Specifying the physical aspects and requirements for automated material handling and transport, while of utmost importance, is not enough for operating an automated factory. Communication to and from the physical equipment, host and automated material handling system (AMHS) server program, traditionally called the material control system (MCS), must be specified. The communication with the MCS to the other parts of the manufacturing execution system (MES) also must be specified.
These requirements are described at a conceptual level in the Global Joint Guidelines and at a specification level in SEMI documents E82, E88, and E102. E82, the Intra Bay AMHS SEM specification (IBSEM), specifies communication between the physical transportation systems and the MCS. E88, the specification for AMHS Storage SEM (Stocker SEM), specifies communication between stockers and the MCS. E102, CIM Framework Material Transport and Storage Component, specifies communication between the MCS and the MES. Figure 3 shows the logical architecture of the factory system, and the material transport and control system
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The last, but certainly not the least important, aspect of material transport that has been defined is the communication from the physical AMHS transportation system to the physical production equipment. The imple- mentation details are specified in SEMI E84, which is a handshake mechanism that ensures safe transfer of carriers between AMHS transport vehicles and production equipment.
Material handling at the equipment
The automated material handling requirements are defined primarily in SEMI standards E87, E90 and E94. E87 is the specification for Carrier Management, and it defines the behavior and communication requirements for notifying equipment of future delivery of carriers, reserving load ports, reading and verifying carrier IDs and slot maps, and moving carriers to the delivery position. It also provides a method for the host to inform the equipment of the specific wafer ID in a specific slot. This record of wafer ID and FOUP ID is called the ContentMap. E90 is the specification for Substrate Tracking. This standard defines the methods for tracking both substrates and the locations that can hold them. E94 is the specification for control jobs; this standard defines the methods for defining the order of process jobs within a carrier as well as the source and destination of the wafers. This capability allows equipment to sort wafers as specifically instructed by the host or by predefined criteria. This reduces the number of wafer sorters required in the fab.
The combination of these standards enables common behavior across all production equipment. This in turn enables a consistent interface to the factory host. As a result, the equipment can be integrated into the factory and run with little or no human input required for handling the material.
Processing, process control and recipe management
A completely automated fab requires equipment not only to handle the material automatically but to start and stop processing, collect process data, change controllable variables and select recipes as required for the product. Each of these enables tighter control over individual wafer processing. In addition, these functions provide a means to reduce the use of test and monitor wafers. The equipment must do these things in a standard way so the overall factory system can recognize and provide the services immediately as the equipment requires them. SEMI standards E5, E30, E37, E40, E54, E87, E93, and E94 address these requirements.
E5, the SEMI Equipment Communication Standard II (message content), and E30, the Generic Equipment Model, have been established as the method through which the factory system and the equipment communicate. E37, High Speed Message System, provides the bandwidth needed for the large amounts of data that go to and from the equipment. E40, Specification for Processing Management, enables multiple different processes to be defined for the substrates within one carrier. E54, Sensor Actuator Network Standard, enables equipment to tie the many components needed for automated process control. E87, as discussed above, provides methods for the host to inform the equipment of specific wafer ID. E93 is a factory systems-level standard that enables plugging various process control software packages into the factory system. This creates the ability to monitor equipment for fault detection as well as methods for changing recipe variables. These recipe variables will be communicated to the equipment through the methods defined in these equipment-level standards. E94 enables control jobs as discussed above.
Material tracking
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Dispatching
Automated dispatching fulfills the requirement to maintain high tool utilization. Automated and accurate material tracking enable automated dispatching. Automated dispatching means no operator will be required to ask what is next for a resource, or where a lot should go next. When events from the tool indicate to the MES that a piece of equipment has completed processing on a carrier, the dispatching component will indicate where this carrier should be delivered, be it a stocker or another production tool. The dispatching component also will recommend what the equipment should do next: process another carrier, set up for different processing or wait for preventive maintenance.
Fully automated scenario
The sequence of product movement in a fully automated factory is shown in Figure 4, and the Table details how SEMI standards support the sequence.
| Fully Automated Sequence | |||
| Step number | Action | SEMI Standard | CIM Global Joint Guideline number |
| 1 | Finish processing, sorting | E87, E90, E94 | 3.1, 3.3, 3.5, 3.8, 4.4, 4.6, 4.7, 5.1, 7.1, 7.3 |
| 2 | Dispatching for carrier | Draft document 2827b | 7.1, 7.4 |
| 3 | FOUP picked up by the intrabay AMHS | E82, E84, E87, E102 | 2.1, 2.2, 2.3, 2.5, 3.1, 3.3, 4.1, 6.1, 7.1, 7.2, 7.3 |
| 4 | FOUP delivered to stocker A | E82, E84, E88, E102 | 6.1, 7.1, 7.2 |
| 5 | FOUP picked up by interbay AMHS | E82, E88, E102 | 6.1, 7.1, 7.2 |
| 6 | FOUP delivered to stocker B | E82, E88, E102 | 6.1, 7.1, 7.2 |
| 7 | Dispatching for equipment | Draft document 2827b | 7.1, 7.4 |
| 8 | FOUP picked up by intrabay AMHS | E82, E84, E88, E102 | 2.1, 2.2, 2.3, 2.5, 3.1, 3.3, 4.1, 6.1, 7.1, 7.2 |
| 9 | FOUP delivered to equipment | E82, E84, E87, E102 | 2.1, 2.2, 2.3, 2.5, 3.1, 3.3, 4.1, 6.1, 7.1, 7.3 |
| 10 | ID read and verified | E87, E99 | 2.6, 2.7, 3.8, 7.1, 7.3 |
| 11 | Equipment moves carrier to internal buffer position; slot map read and verified | E87 | 3.6, 3.7, 4.1, 4.3, 7.3 |
| 12 | Equipment begins processing | E40, E90, E94 | 5.1, 5.2, 7.1, 7.3 |
When tool A is finished processing wafers, sorting takes place at that tool. Wafers are placed in a different FOUP, and any change in the ordering of the wafers is recorded. Next, the dispatcher chooses the destination for the lot, stocker B. The FOUP is then picked up by the intrabay AMHS and delivered to stocker A. The interbay AMHS takes the FOUP from stocker A and delivers it to stocker B. The dispatcher chooses what is next for tool B, and the intrabay AMHS for tool B delivers the FOUP from the stocker to the tool. The ID for the FOUP is read and verified; then the FOUP is moved to the internal buffer position. After the slot map is read and verified, processing begins.
Conclusion
SEMI standards now exist that support automated material movement about the fab and processing within the equipment. The Global Joint Guidelines focused the efforts on creation of the SEMI standards. These standards provide common handoffs of material from the automated delivery system to the process equipment, and management of the processing at the process equipment. These supporting automation standards provide the opportunity for semiconductor fabs to realize the gains intended by the International Technology Roadmap for Semiconductors.
Karl Gartland graduated from the University of Massachusetts with a bachelor's degree in chemistry in 1981. He was a process engineer at IBM in support of metal levels for nine years, during which IBM built the first 200 mm semiconductor manufacturing line. He received his master's degree in manufacturing systems engineering from Lehigh University in 1992. He represented IBM at SEMATECH and I300I, and has been an International SEMATECH and Global CIM study group co-chair and contributing author to the CIM Global Joint guidelines since 1998. He currently is the 300 mm transition coordinator for IBM, the SEMI carrier management task force leader, and a member of Semiconductor International's editorial advisory board.Ed Sherwood graduated from Farleigh Dickinson University with a bachelor's degree in Electrical Engineering Technology in 1979. He has been an equipment engineer at IBM in support of IBM semiconductor manufacturing lines. He has represented IBM at I300I Factory Integration Working Groups and has been a contributing author to the Global Joint guidelines. He is the 300 mm factory technology integration project manager for IBM.
REFERENCES
- International Technology Roadmap for Semiconductors, 1999.
- Global Joint Guidance for 300 mm Semiconductor Factories, I300I and J300, 1997.
- CIM Global Joint Guidelines for 300 mm Semiconductor Factories, Release 5, International Sematech and J300E.
- I300I Factory Guidelines, Version 4.2.
