As devices get smaller and the fabrication plants get larger, the purity of the water required for ultrapure water systems increases. In terms of water reuse, the industry has relatively conservative attitudes towards recycling water for ultrapure water applications, but wastewater is treated and reused for cooling and other less critical purposes. Besides semiconductors, two other silicon-based sectors of the microelectronics industry need large volumes of highly pure water: flat panel displays (FPD) and photovoltaics (PV). Although, both sectors are in the process of maturing we anticipate that the increasing complexity of FPD and PV devices will create demand for even higher purity water.
Microelectronics is a rapidly evolving industry which produces a wide range of devices for the modern world. Common products include microchips (also called “computer chips” or “integrated circuits”), solar cells, and the flat panel displays. Microelectronics devices are produced in fabrication plants (fabs) and large volumes of ultrapure water (UPW) are required during the production process. The industry also generates complex wastewater streams which contain toxic contaminants, e.g. a wide range of acids and metals which require special treatment prior to discharge.
Water treatment market drivers in microelectronics
There are a number of drivers that shape the water treatment requirements of the microelectronics industry:
Process water requirements
Two grades of water are used in fabs: UPW, which comes into direct contact with the device being produced, and other process water, which is used for other equipment related to the manufacturing process. UPW is used in different steps of the manufacturing process and constitutes the majority of the water used in a plant.
Desalination technologies for process water
UPW treatment for semiconductor manufacturing has developed rapidly over the last 20 years. At present, the existing treatment technologies are able to meet the water quality requirements for the current generation of devices. The individual technologies are likely to remain the same for the foreseeable future. However, the exact treatment train used in a UPW system will depend on a number of factors: feedwater quality, device line-width, specific contaminants of concern, production requirements and end-user confidence levels. For example, if an end-user wishes to operate a facility 24 hours per day all year round, it might be prudent to install duplicate selected equipment to avoid disruption of the production process in case of equipment failure. The plant operator might also install more specific equipment to further increase confidence levels in the UPW production process.
The semiconductor manufacturing process uses a wide range of slurries and chemicals which generate very contaminated wastewater. Although the industry does not use toxic chemicals such as cyanide and lead, it uses other compounds which if left untreated cause environmental pollution and pose a risk to human health. For example, the industry uses high volumes of corrosive hydrofluoric acid (HF) for cleaning and photosensitive treatments, which in high concentrations can dissolve many materials. Other agents used during the manufacturing process include ammonium hydroxide ( NH4OH), hydrogen peroxide (H2O2), hydrochloric acid (HCl), sulphuric acid (H2SO4) or phosphoric acid (H3PO4 ). The wastewater includes mixtures of these chemicals, together with other contaminants that result from the manufacturing processes, such as traces of nickel, copper, cobalt, titanium, fluoride, silica, ammonia, and many other organic and inorganic compounds.
Water reuse strategies
Fabs offer a wide range of opportunities for water reuse. However the suitability of a wastewater stream for reuse depends on the level of contamination, and this varies between processes, as well as depending on the individual steps of particular manufacturing processes. For example, during the CMP process, only the wastewater from two of the three steps is suitable for water reuse.
Wastewater treatment and water reuse technologies
No specific wastewater treatment technologies have been developed primarily for the microelectronics industry, and the conventional technologies used are very similar to those used in other industries. The following figure lists the most common wastewater treatment methods employed by the industry.
Supply chain analysis
The semiconductor industry is very conservative, and is therefore a difficult market to enter. Microelectronics manufacturers (also called “end-users”) are looking for water treatment companies which clearly understand their needs and requirements and will not jeopardise their production yield. Manufacturers prefer long-term relationships and are open to change only when it is seen as absolutely necessary.
According to the SEMI World Fab Forecast dataset (the industry standard for semiconductor fab information), the current design capacity of the semiconductor industry is 21.4 million wafers/month in 200 mm wafer equivalent. Fabs currently produce microchips on wafers ranging from 50 mm to 300 mm in diameter. 450 mm wafer fabs are currently in planning stages and a first commercial plant is likely to be built within the next few years.
Our market forecast is underpinned by the SEMI World Fab Forecast, May 2012 edition, which details capital expenditure, capacity, technology, geometry and products on a fab-by-fab basis. The dataset is the de-facto data source for information about the semiconductor industry. It contains 1,166 existing fabs, 106 fabs starting operation and 53 fabs starting construction, with expected online dates which we used to inform our forecast.