The 450 mm Road is Paved with Complexity, Uncertainty
By Jonathan Davis, president, Global Semiconductor Business, SEMI
Important developments are unfolding in the industry's analysis of a possible wafer size transition. Moving leading-edge semiconductor manufacturing to 450mm wafers is one of the most complex and challenging issues in our industry. While advocates maintain that larger wafers are needed to keep pace with Moore��?s Law, opponents argue that larger wafers will detract from innovation and negatively impact profitability��? draining precious R&D funding away from critical advances in scaling, manufacturing flexibility, and cycle time improvements.
Switching to 450 mm wafer manufacturing will involve difficult decisions involving timing, funding mechanisms and planning processes. The industry will miss the ISMI 2012 target date, but new target dates have not been firmly established. Funding mechanisms for the multi-billion dollar R&D price tag for a 450 mm wafer transition also have not been established? And, moving leading edge manufacturing to 450mm calls into questions how the industry makes informed, collective decisions on issues impacting multiple chip makers and a global supply chain? Over the past several months, progress has occurred on each of these issues, but important questions and significant uncertainties remain.
SEMI is involved in moving the debate forward by advocating for a detailed economic and supply chain cost analysis before moving to implement 450 mm manufacturing. It has worked on the issue through the SEMI Standards 450 mm Task Force and publication of the first 450 mm standards for wafer carriers and load ports. Significant progress has also been made by the International SEMATECH Manufacturing Initiative (ISMI) which is facilitating industry readiness through wafer handling pilot lines, sample wafer loans, and other activities. Other R&D consortia and many individual companies are also ready for the hard work involved in scientific research and product development.
Scaling Up
In 2005, ISMI reported that wafer processing cost curves were shifting unfavorably so that the Moore��?s Law could not be maintained unless wafer size increased. Later in 2005, the SEMI and SEMATECH Board of Directors members met for the first time to discuss an industry-wide transition to larger wafers.
Many SEMI members recall the difficult and costly transition to 300 mm wafers, and they formed the Equipment Productivity Working Group (EPWG) to conduct their own simulation, survey, and modeling to analyze the issues supporting the cost reduction contribution of a wafer scale-up. After two years of open, collaborative analysis, the EPWG concluded in a White Paper that 450 mm wafer scale-up represents a low-return, high-risk investment opportunity for the entire semiconductor ecosystem[1].
However, the obvious upside to scaling up is improved silicon productivity. This remains the primary argument for wafer size transitions. Increasing the wafer area increases the number of dies per wafer and leads to a theoretical reduction in die cost of approximately 30 percent if all other costs remain constant. The semiconductor industry has increased wafer size about once every 10 years. In 1991, the industry first started using 200 mm wafers, switching to 300 mm wafers in 2001. ISMI��?s original goal of transitioning to 450 mm wafers in 2012 would be consistent with that industry timeline.
The semiconductor industry also faces increasing difficult challenges in scaling, another critical issue. Critics of 450 point out that focusing on wafer size increases represents the single most disruptive type of investment the industry could undertake, thus detracting from scaling issues. To implement 450 mm, every piece of process and automation equipment must be redesigned, from crystal growing to final test.
Some argue that technology requirements for 450 mm tools far exceed a simple linear size expansion of existing 300 mm tools. Wafer bow and flatness, wafer thermal expansion, loading and wavelength affects, new chamber designs, and other impacts will fundamentally alter the physics of patterning, deposition, etch, planarization, and other processes. Each of today��?s 300 mm processes require nearly 1,000 steps and each will need ground-up scientific analysis and reengineering. Data processing and metrology requirements of the larger wafers will slow cycle time, and yield will be profoundly affected.
Figure 1: Companies Manufacturing Semiconductors by Wafer Size
However, significant progress has been made and most observers feel the issue is no longer a matter of ��?if,��? but rather a matter of ��?when.��? Funding a transition remains a difficult challenge, but new funding models are starting to emerge.
ISMI and SEMI: Involved in Getting the Industry Ready
ISMI is actively involved in supporting 450 mm wafer development and material handling requirements through a number of programs and demonstration projects. They have created a ��?wafer bank��? to lend test wafers to equipment developers, developed an interoperability test bed to support automation and material handling demonstrations, and created a set of equipment performance and EHS documents. ISMI has completed prototype testing of 450 mm factory integration equipment, including lab testing focused on 12 mm pitch FOUPs, MACs and load ports. They have evaluated multiple personal guided vehicles (PGVs) for wafer handling and verified pallet requirements for MAC shipping. Later this year, ISMI will demonstrate automated materials handling system (AMHS) components including new 450 mm stockers and overhead hoist transport systems.
ISMI has also created preliminary ISMI 450 mm vacuum platform guidelines and published EQP software guidelines, but final evaluation of the feasibility of vacuum platform standardization won��?t begin until 2013, according to ISMI.
SEMI International Standards development has also made progress to enable pilot development and provide a platform for future development work. In July 2010, SEMI M76 was adopted by the industry to detail test wafer requirements for various applications such as lithography, patterning, thermal processes, films and deposition. Also in July 2010, SEMI passed E156 that relates to the storage and transport of 450 mm wafer carriers in a semiconductor factory.
Eventually, a 450 mm pilot system needs to be developed. Certainly, these material handling demonstrations, standards and guidelines activities are necessary precursors for the pilot system, but critical process technology analysis has not begun. While wafer polishing processes have improved and particle levels have been dramatically reduced, wafer quality remains below the threshold for process research and development. Surface metal metrology is still in development and inspection equipment is not yet online. ISMI claims there are no technical ��?shows stoppers��? but the fact remains that the hard scientific work has not yet begun.
Funding Model Questions Remain
Economic justification for a 450 mm transition includes questions on funding models. In the SEMI White Paper study, equipment suppliers claimed the 300 mm transition benefitted only chip makers, and the supply chain has yet to recoup their R&D investment from the last wafer scale-up. SEMI estimated that the R&D for the 300 mm transition at over $22 billion [1]. In 2005, SEMI asserted that industry was facing an R&D funding gap that threatened the continuation of Moore��?s Law-related cost reductions. In 2006, SEMI claimed that ��?Before a successful transition to 450 mm can be conceived, the industry will need to fund the investment in a way that provides a reasonable return to the supply infrastructure whose participation will be required. At this time, it is not clear that there is a benefit to the industry that outweighs the increased cost of the equipment required.��?
In July 2010, ISMI acknowledged that the historical financial risk model for wafer- size transition funding is no longer relevant, and that ��?risk-sharing with tool suppliers is expected to realize the 450mm transition.��? ISMI��?s planned mechanism is some type of cost sharing to lower the financial risk for tool and technology suppliers.
ISMI has announced that they will engage in discussions and negotiations to support funding of R&D development, but how this approach will roll out across the supply chain is vague. Presumably, ISMI will enter into a case-by-case funding approach with every supplier of every key tool set, or some subset of suppliers based on yet-to-be determined considerations. While much is still not known about scope, scale and strategy of this ISMI funding approach, it is a radical departure from traditional consortia funding and roadmap development models.
As we examine the issue of 450 mm, our goal remains the continued growth and proliferation of electronic goods and services. The key driver for this growth is the industry��?s push to keep up with Moore��?s Law, dramatically reducing costs. Fundamental to this growth is a highly-refined collaborative process such as the ITRS and SEMI standards, plus industry consortia to finance pre-competitive R&D. How will these models and mechanisms for collaboration operate in the coming years to support a transition to 450 mm wafers? Let us know what you think.
[1] SEMI White Paper, Equipment Suppliers��? Productivity Working Group 450 mm Economic
Findings and Conclusions, June 2008
[2] SEMI White Paper, Equipment Suppliers��? Productivity Working Group 450 mm Economic
Findings and Conclusions, June 2008
