300-mm factory trends
10/01/1997
Frank Robertson, International 300-mm Initiative, Austin, Texas
The opportunity to minimize the cost of 300-mm factories through standardization is being pursued by a number of global organizations. The International 300-mm Initiative (I300I) and the Japan 300-mm Semiconductor Technology Conference (J300) have cooperated to establish a set of factory guidelines that define end-user requirements to the standards development process in Semiconductor Equipment and Materials International (Semi). The capabilities required to support 300-mm factory systems must be designed into the equipment from the beginning to minimize costs for development and operations. This article surveys 300-mm factory trends. The following article, by Semi president Stanley Myers, discusses the details of the guidance document.
The semiconductor industry continues its historic trend of increasing productivity according to Moore's Law. In addition to the well-known increase in performance of devices through feature-size scaling, productivity growth has come from periodic increases in wafer diameter and improved equipment productivity and product yields. The industry's current transition to 300-mm embodies all of these elements.
Ergonomic considerations due to the size and weight of 300-mm wafers will drive adoption of Automated Material Handling Systems (AMHS). Effective use of costly manufacturing assets also demands automation and computer integrated manufacturing (CIM) systems. Limiting the number of tool configurations and standardizing both mechanical and communication interfaces will minimize the cost of these capabilities.
Factory approaches
Because no one company or region can support the cost of the 300-mm transition, there has been unprecedented global cooperation to define and implement the required capabilities. Industry groups have developed a good understanding of the projected operating methods for 300-mm factories. This knowledge has reduced the number of equipment configurations that must be developed.
Two major product delivery paths have been defined for 300-mm manufacturing lines. Open cassettes (OC) can be transported by automatic guided vehicles (AGV), while front opening unified pods (FOUP) are compatible with both AGV and overhead track (OHT). The I300I members suggest that pod door opener and ambient control systems, internal to the tool to support minienvironments using FOUP, should be integrated into 300-mm designs at the first generation. J300 device companies have stated that they may use a mix of open cassettes and pods. Both groups have agreed on a goal of immediate compatibility between OC and FOUP with respect to 300-mm loadport interfaces.
Factory productivity
To maximize the output of any factory, use of capital assets must be optimized in order to load critical tools fully while balancing the rest for line flow. In support of this requirement, 300-mm tools must be able to run continuously as product lots are exchanged. For most tools, this guideline means that one additional wafer carrier position must be provided for a carrier immediately ready to follow the one in process. Large-batch or high-throughput equipment may require more than one local buffer position for continuous operation. Some companies may specify local buffer capacity for a given time, dependent on tool throughput.
300-mm factories must be populated with equipment that rapidly achieves equipment availability greater than 90%. Tool accommodation standards should be followed to ensure that facilities are ready for minimum installation cost and time. Committee members would prefer to install tools with sides abutting adjacent tools for dense packing, and perform maintenance from the rear. If allowing access to one side improves availability enough to offer a cost advantage, mirror image tools can be abutted on one side.
CIM to improve productivity includes factory communications to support yield management for, first, 0.25 micron, then 0.18-micron devices and beyond. Compliance with SECS II, GEM, HSMS, and other communications protocols is required for all equipment. Process, metrology, and parametric test equipment must interact with probe and final test to correlate process history and die location with device performance and yield.
Conclusion
Global device companies are defining the equipment capabilities and factory systems required to achieve productive manufacturing on 300-mm wafers. A reduced set of carriers, interfaces, and communications selected for a high degree of compatibility among solutions will support the projected factory approaches. Standards are being developed to reflect these end-user needs and provide suppliers with the means to achieve interoperability among systems and reduce development costs. Compliance with these standards and the integration of the capabilities into the early designs of 300-mm equipment will minimize conversion costs.
Bibliography
- "I300I Guidelines on 300-mm Process Tool Mechanical Interfaces for Wafer Lot Delivery, Buffering, and Loading" September 1996.
- J300 Second Lecture Document on "IC Factory Design for 300-mm Wafer Line Standardizing Study" December 1996.
- I300I / J300 "Global Joint Guidance for 300-mm Semiconductor Factories," July 1997.
- Semi Standards for Safety, Ergonomics, Communications, Facilities, Carriers and Interfaces for 300 mm, updated Spring 1997.
Frank Robertson is vice president and general manager of the International 300-mm Initiative. In this capacity, he works with the consortium's 13 member companies to define its technical programs for standards, performance metrics, and demonstration of equipment and materials. His external focus is coordination of the I300I programs with other groups working on 300 mm, such as Japan's Selete, Semi, and the European Semiconductor Equipment Assessment program. Before joining I300I, he directed Sematech's Factory Integration and Materials & Bulk Processes divisions. E-mail [email protected].