Feb 17, 2010
Semiconductor chips power ahead
Lightweight laptops, dinky mobile phones and pocket-sized digital cameras: all commonplace technology today, thanks to the huge advances in the semiconductor industry. But these advances are accompanied by an environmental cost. A new lifecycle analysis of hi-tech semiconductor chips reveals how their environmental impact has changed over time, and investigates the most effective way of reducing that impact.
For the last 50 years or so, the number of components that can be squeezed onto a chip has doubled approximately every two years. This exponential shrinking is known as "Moore's law"; it is this that has driven the production of ever smaller and faster computers, with ever-greater amounts of memory, along with multi-functional digital cameras and phones.
Without a doubt this effect has been good for the world economy but this mounting speed and productivity has also been accompanied by an increased drain on resources, consumption of energy and generation of pollutants.
Sarah Boyd, from the University of California at Berkeley, US, and her colleagues assessed the life-cycle impact of semiconductor chips between 1995 and 2010. The researchers consider a production scenario with wafer manufacturing in Santa Clara, California, using chemicals, equipment and construction materials produced in the US, while packing and testing are carried out 3000 miles away.
The scientists model the impacts associated with fabrication, infrastructure, transportation and use of the chips, assuming a 6000-hour lifetime for each device. In each case they consider global-warming potential, acidification, eutrophication, ground-level ozone (smog) formation, potential human cancer and non-cancer health effects, ecotoxicity and water use.
Most strikingly the results show that electricity consumption associated with semiconductors has risen dramatically over the last fifteen years, increasing carbon dioxide emissions by approximately tenfold. "The increased computational power has allowed many applications and services to occur via information technology that weren't possible in 1995," Boyd told environmentalresearchweb. "Due to the increased adoption and application of computing, total energy use for computing, society-wide has increased over the same time period."
Today the majority of this power (92%) is drawn when the chip is in use and only a small fraction is associated with the fabrication and transportation of the device. In the past a larger proportion of energy – over 25% – was used in production of the chip. "Even when you consider a realistic scenario of a chip using less than 20% of its maximum power during normal operation, the total energy consumed during the use phase really adds up," says Boyd.
The story is similar for smog formation, acidification and health and eutrophication impacts, with the large power demand of modern devices responsible for the majority of chemical emissions that cause these effects.
However, things would be a lot worse if it wasn't for the reduction in use of perfluorocarbons – exceedingly potent greenhouse gases – in production. "The global-warming potential associated with perflurocarbon (PFC) emissions would be huge if it weren't for the introduction of remote plasma generation, which reduced PFC use, and the adoption of PFC abatement in industry, which cuts PFC emissions by about 99%," says Boyd, whose findings are published in the journal Environmental Research Letters.
Semiconductor manufacturers in most of the top semiconductor-producing nations have formally committed to PFC goals through the World Semiconductor Council PFC Emissions Reduction Agreement, and are on target to meet those goals. However, while these manufacturers, in the EU, Japan, the US, Korea and Taiwan have all committed to PFC-emissions controls, the industrial members in some of the fastest growing semiconductor-producing nations, specifically Singapore, China and Malaysia, have not. "It is important that these younger semiconductor manufacturers also commit to this agreement, to prevent uncontrolled emissions of these powerful greenhouse-warming gases," says Boyd.
Based on their results, Boyd and her colleagues believe that reducing power consumption of devices while they are in use is the most effective way of limiting their environmental impact. "The actual employment, by the user, of energy-saving modes on computers and monitors probably has allowed, or can allow, the greatest energy savings," says Boyd. "Advanced energy-saving modes have become standard on desktops and laptops but their implementation is ultimately up to the user."
In addition, more efficient power supplies in computers could make a significant difference, as would further advances in chip-level power management.
About the author
Kate Ravilious is a contributing editor to environmentalresearchweb.