Abatement technology is finding increasing use in today’s hi-tech industries. Susan Birks talked to vacuum and abatement specialist Edwards about the growing market and its new technologies
Everyday life has been transformed over the past 20 years, first with the revolution in semiconductor manufacturing that brought us cheap computers, and then with the introduction of micro-electronic devices leading to MP3 players, iPhones, etc. Now new hi-tech inventions, such as flat panels and solid state lighting using light emitting diodes (LED) promise greater changes in the future.
New hi-tech production facilities are being built around the world to satisfy demand for these new products, and many of them require contamination-free environments and special atmospheres and cleanrooms. But like any other industry the hi-tech sector is affected by the need to reduce carbon emissions and cut greenhouse gases.
In particular, perfluorinated compounds (PFCs) used extensively in semiconductor manufacturing have been implicated in global warming. Integrated Circuit (IC) companies have been evaluating the most cost-effective ways to meet the World Semiconductor Council’s 2010 objective of reducing PFC emissions to below 90% of what the industry produced in 1995.
The technologies, such as imaging, deposition and etching, used by these industries can give rise to other undesirable toxic and corrosive gases such as SiH4, CF4 and SF6. In LED production, the gases that arise from metal-organic chemical vapour deposition (MOCVD) processes have to be removed.
As a result, developed alongside these hi-tech processes are abatement technologies that can treat and remove these undesirable products to ensure they are not simply evacuated to the environment.
Leading exponent of vacuum and abatement technology, Edwards is one such company trying to innovate in line with the dramatic pace at which these manufacturing processes are introduced.
Edwards’ history in the development of vacuum technology means it has worked with pharmaceutical, chemical, scientific, process, glass coating and food packaging industries for many years. More recently the company has been successful in integrating its vacuum technology with abatement equipment and it now sees gas abatement as a key growth area.
Despite the economic slow-down and the cyclical nature of the semicon industry, which experienced a dip in 2008/9, Edwards is expecting a record year for sales in its abatement technology in 2010, being driven in part by massive growth in the LED sector. Solar panels is also a market in which it expects to see continued growth.
There are three main abatement technologies currently available to the semiconductor industry: catalytic decomposition, combustion and plasma.
In the field of combustion gas abatement, Edwards has developed the Atlas range of solutions for semiconductor manufacturers. The range is described as having low fuel consumption compared with previous generation gas abatement devices and uses inward-fired combustor technology to achieve reduced costs of ownership.
More recently the company has produced the Zenith series that addresses the vacuum and abatement demands for advanced semiconductor processing at 60nm and smaller.
Edwards also offers electrically heated oxidation systems for the removal of pyrophoric and acidic gases commonly found in semiconductor applications; as well as the Gas Reactor Column series of low-cost, point-of-use, dry abatement systems for semiconductor processing; and point-of-use water absorption scrubbers suitable for the treatment of exhaust streams containing water-soluble and water-reactive gases.
Rapid change
Innovation is key to Edwards’ survival because manufacturing processes change so rapidly. Furthermore, every company’s process produces its own cocktail of gases, so Edwards works alongside them to find out what those gases are and the most efficient process for removing them. Much of the r&d work arising from this co-operation is carried out at the company’s site in Bristol, UK.
The solar and flat panel sectors have slightly different requirements, and Edwards has developed the Spectra ZW for abating deposition and cleaning gases used in high gas flow chemical vapour deposition process steps. In the Spectra, high-flow particulate and acid gas capture and processing are provided in one stand-alone system.
And for use in LED manufacture, the Spectra G is capable of treating all exhaust gases from multiple MOCVD production tools and its combustion technology allows abatement of NH3 while minimising NOx emissions.
Plasma solution
A further innovation from the company is the development of plasma exhaust management solutions. These are specifically designed for both the CVD and etch markets and the technology uses an energy efficient microwave plasma in a carefully controlled chemical environment and an integrated wet scrubber to reduce fab greenhouse gas emissions by as much as 95% over a wide range of total flow rates and perfluoro compound (PFC) concentrations.
Plasma abatement has a significantly lower cost of ownership than fuelled abatement, resulting from lower costs for energy, consumables and maintenance. At the same time, its high-density plasma delivers more energy to the abatement process itself, ensuring effective destruction of both greenhouse gases and potentially toxic by-products.
To ensure future innovations are forthcoming, Edwards recently joined the International SEMATECH Manufacturing Initiative (ISMI) Environment, Safety and Health (ESH) Technology Center.
Within the Center, Edwards will collaborate with hundreds of ESH experts and consultants from around the world to develop data-driven solutions in areas such as energy and resource conservation, chemical management, and industry response to climate change.
ISMI launched its ESH Technology Center in 2009 to find and implement green technologies that reduce energy consumption and promote greater productivity in manufacturing.
Despite the spectre of an economic slowdown, Edwards sees a bright future, with the rapid deployment of new technologies such as LED and flat panels increasing growth for its abatement equipment.
Abatement technology by sectorClean semiconductor manufacture
Wafer size has gradually increased to improve throughput and reduce costs. Current state-of-the-art fab is considered to be 300mm (12in), with the next standard projected to be 450mm (18in). As wafers get bigger, gas volumes get bigger.
Addressing gas abatement challenges arising from dielectric and polysilicon etch processes used in semiconductor manufacturing, Edwards’ Sirius 6000 system reduces fab greenhouse gas emissions by 95% over a wide range of total flow rates and perfluorocompound (PFC) concentrations.
It uses an energy efficient microwave plasma in a carefully controlled chemical environment and an integrated wet scrubber to reduce fab greenhouse gas emissions. High-density plasma delivers more energy to abatement process, reduces PFC gases to hydrogen fluoride (HF), and prevents creation of harmful by-products, such as carbon tetrafluoride (CF4).
With the change from traditional PFC gases to nitrogen fluoride (NF3) remote plasma cleaning for chemical vapour deposition (CVD) chambers, etch processes have become the major PFC emitters in state-of-the-art 300mm fabs.
The plasma reduces PFC gases to hydrogen fluoride (HF) and prevents the creation of harmful by-products, such as carbon tetrafluoride (CF4). The hydrofluoric acid and any other remaining byproducts are then removed from the exhaust stream in the integrated wet scrubber.
Flat panel displays see rapid growth
Flat panels are a growth area
The most ubiquitous flat panel technology in use today is Active Matrix, Thin Film Transistor, LCD (AM-TFT-LCD), which uses similar processes to fabricate the transistor switches, capacitors and conductors as are used for microchip semiconductors, but on glass substrates rather than silicon wafers.
These vacuum-based processes include:
• Physical Vapour Deposition (PVD) – sputter coating for metal and transparent conducting oxide (TCO) electrodes
• Plasma Enhanced Chemical Vapour Deposition (PECVD) – growth of the amorphous silicon and SiN thin film transistor structures
• Plasma dry etching – etch back of the fine structure using photolithography techniques
Several panels are fabricated on one substrate. After the assembled substrates are separated into individual panels, the empty cells are filled with liquid crystal material by vacuum injection and then sealed.
Increasing the number of panels produced on a single substrate increases the yield of the very complex fabrication processes and the panel cost can be reduced. Also, user demand has steadily increased the average panel size. These two drivers have meant that the substrate size has steadily increased – requiring the continual design and construction of new generations of process equipment including vacuum pumps and their abatement systems.
Solar cells
The demand for renewable energy has seen photovoltaic production of solar cells increase by an average of more than 20% each year since 2002. At the end of 2009, the cumulative global PV installations surpassed 21,000 megawatts. The main markets are Japan, the US and Germany.
Some of the fluorinated gases used in crystalline silicon photovoltaic solar cell and film silicon module manufacturing (CF4, C2F6, SF6 and NF3) have a high global warming potential. These gases can be used in texturing, phosphorous silicate glass removal (PSG), edge isolation and reactor cleaning operations.
LED production
Solid State Lighting is the new, energy-saving lighting solution that uses high brightness Light Emitting Diodes (LEDs). Current market opportunities driving the expansion in LED production already include laptop computers, as well as liquid crystal display (LCD) backlighting used in LED TVs and automotive applications.
Shorter wavelength LEDs (green–blue) use nitride-based materials while the longer wavelengths (red–yellow) use phosphide-based materials. Each material poses unique abatement challenges.