Trends in Subfab Energy Consumption and Emissions Control
Andreas Neuber, Maxime Cayer, Shaun Crawford and Andrew Herbert
The semiconductor industry has made great advances over the last few decades, but multiple challenges must be overcome for that progress to continue. Among them is the need for companies to move along a sustainable growth path. That need is driven by the increasingly short supply and growing expense of resources critical for semiconductor manufacturing, such as water and power.
What does this mean for the semiconductor manufacturing industry going forward? Energy-saving technologies and products may have a significant positive impact, and are widely recognized as useful ways to promote sustainable growth. Variable-frequency ICs to drive pump motors are one example. Another is the synchronization of fab and subfab operations to optimize subfab resource consumption with no risk to the manufacturing process or throughput.
Energy savings will assume an even greater importance in the years ahead. Many regions now require that power and resource consumption, and emissions, stay at an even level as production capacity increases. And this is occurring as cost-reduction pressures in all phases of semiconductor manufacturing are stronger than ever.
The good news is that energy conservation, reduction of greenhouse gas emissions (GHGs) and cost reductions do not necessarily contradict one another. For example, the high operating costs to effectively abate environmentally harmful perfluorocarbon (PFC) gases can be reduced by applying alternative technologies, such as pre-pump plasma abatement. Pre-pump abatement reduces power consumption and generation of typical byproducts such as nitrogen oxides (NOx).
However, such solutions must be available both for new tools and for existing fabs with reasonable rates of return on investment. The ability to achieve an attractive ROI within one to three years depends on many factors—the cost of energy and other resources being a major component. Also, measures implemented to save energy and resources must not negatively impact manufacturing or result in increased safety or fab operation risks.
Today, the focus on saving energy and resources has shifted from facility operations to the subfab, for several reasons:
- The subfab currently consumes more energy and resources than any other part of the production facility (see figure 1).
- Most fabs no longer have much low-hanging fruit—easy opportunities to drive improvements in resource efficiency—thanks to improvements already made over the past few years in facility operation.
- Because changes in the subfab apply only to auxiliary processes, it is possible to retrofit equipment or implement other changes in existing semiconductor subfabs without having to requalify manufacturing processes.
Figure 1 shows the power consumption of a fab by specific application, while figure 2 shows the major distribution of power in a fab. Note that figure 1 is incomplete to some extent, because, in addition, the consumption of other utilities is primarily driven by the variable needs of the manufacturing equipment.
Figure 1. Breakdown of power consumption in a fab by specific application.
Figure 2: Distribution of power consumption in a fab.
If one also considers indirect power consumption, based on the SEMI S23 Guide for Conservation of Energy, Utilities and Materials, the portion attributable to manufacturing equipment would be even larger. More than 80% of a fab’s power consumption is driven by the needs of the manufacturing process itself, and only 20% by the infrastructure.
Figure 3 shows the power consumption of key components of a fab’s manufacturing equipment. Dry pumps and abatements are some of the biggest energy and resource consumers. Along with pipe heaters, they are the major components that can be most improved without impacting production, because they are downstream of the process.
Figure 3: Pareto diagram showing the typical power consumption of key components of a fab’s manufacturing equipment.
SYNCHRONIZATION CONSERVES RESOURCES
The Applied Materials iSYS controller is a device that communicates between a wafer processing tool and its support equipment in the subfab. The controller receives data concerning tool and chamber status and the chemistries being run. It then provides signals matched to a chamber’s specific requirements to trigger energy and resource savings in the support equipment, even under high-utilization conditions.
For example, the iSYS controller can reduce the total equivalent power consumption for a dry pump by 3–6% when a tool is at 95–100% utilization. Although specific results vary, in practice the fab-subfab synchronization it enables can reduce overall abatement and dry pump operating costs by up to 10% during high tool utilization. These savings are realized because the iSYS controller ensures the pump and abatement units switch to lower energy usage when wafers are not in production.
More than 1,000 semiconductor manufacturing tools have been connected to iSYS controllers since Applied introduced the device in 2009. The controller also provides real-time reporting capabilities to document energy consumption and savings, and allows users to monitor fluorinated greenhouse gases (F-GHGs) emissions and meet green operation reporting requirements.
In addition, the iSYS controller can help reduce NOx emissions and volatile organic compounds (VOCs) generated by abatement. Other subfab components can be controlled as well, including pipe heaters (indirect savings from reduced N2 flows), O3 generators, local chillers, hot N2 purge units, etc.
While the controller enables savings in normal production mode, when O3 generators are used or when temperatures are changed, the system needs wake-up time to adjust to safe operating conditions. These energy-saving states are called sleep modes.
In addition to having a small footprint, the iSYS controller can easily be retrofitted and implemented, with minimal downtime and no effect on process parameters. Thus, whether a tool is running a process, sitting idle or being cleaned, use of power, gas and water is kept to a minimum—reducing the fab’s carbon footprint and lowering costs.
STATUS, CURRENT ISSUES & FUTURE TRENDS
The importance of fab-subfab synchronization is increasing because more energy is required for abatement of PFC gas and N2O emissions than for typical process gases. This is supported by extensive SEMI standardization efforts for idle and sleep-mode energy conservation; see for example SEMI S23, SEMI E167.1 and .2 (work in progress).
Currently Applied Materials is working to develop further improvements in the synchronized operation of both pumps and abatement. For pumps, the main areas of focus include:
- Independent speed and purge N2 control
- Enabling the use of multiple N2 levels
For abatement, the main areas of focus are:
- Providing increased information about the O2 flowing from the process in order to reduce the need for oxidants in the abatement or in consideration of the caloric value from process gases
- Independent control of the thermal reactor section and water scrubber
- Enabling multiple water-consumption levels depending on the gas-type
- Minimizing unnecessary purge flows
Another major trend in fab operation is the use of large and complex data sets. Subfab automation and data collection are currently lagging in this area, but the iSYS controller can collect information about gas flows as well as information from subfab components. This information can be used for:
- Resource consumption reporting, including equivalent energy consumption
- Reporting GHG emissions by correlating gas consumption, conversion and emission factors, as well as abatement availability
- Reporting of other environmental parameters
- Alarm reporting and management alerts for minor subfab components, e.g. pipe heaters
- Predictive pump maintenance
Figure 4. The Applied Materials iSYS controller gives users real-time data concerning energy consumption and savings, plus the ability to monitor performance and document fluorinated greenhouse gas emissions to meet reporting requirements for green operation.
As energy and other resource costs increase, along with environmental sensitivities and government reporting requirements, it is important for semiconductor manufacturers to develop and implement sustainable manufacturing practices.
Fortunately, synchronizing the operation of a manufacturing tool and its support equipment is a safe, efficient and cost-effective way to save energy and reduce emissions with no negative impact on production.
Applied Materials’ iSYS controller is a key technology that helps semiconductor manufacturers move along a path to sustainable growth by helping them lower costs, reduce environmental impacts and meet government reporting regulations for GHG emissions. It is also a proven abatement solution already in production at more than 30 fabs around the globe.
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