New Design of Hydride Sensors Supports Next Generation Digital and Green Technologies


The global semiconductor industry, and the emerging photovoltaic industry, which is rapidly developing in response to the


pressure for carbon reduction in energy production, has seen hydride gas usage


increase dramatically in the last five years. Hydride gases such as arsine, silane, phosphine, diborane and hydrogen selenide now play a critical part in semiconductor and photovoltaic material manufacturing, but their highly toxic, corrosive and explosive


nature requires extensive safety precautions to ensure safe work environments and properly functioning processes.


The main gases used in the manufacturing processes all exhibit potentially life-threatening characteristics, even in relatively low concentrations. Their specific characteristics are shown in the table below. In addition, they are all extremely flammable with silane and diborane potentially explosive at room temperatures. Stringent monitoring for both life safety and plant protection reasons is therefore essential.


In addition to their life- threatening properties, the hazardous nature of the gases is underlined by their inclusion in NFPA 704, a well-known standard maintained by the US-based


NFPA, the National Fire Protection Association. It defines the "fire diamond" used by emergency personnel to quickly and easily identify the risks posed by nearby hazardous materials. The standard helps determine what specialty equipment should be used, which procedures should be followed and the precautions that should be taken during the initial stages of an emergency response.


Gas Characteristics Arsine


Formula Industries


AsH3 Silane SiH4 Health Hazards 42


Rating (1 – 5) Ingestion route


Physical characteristics Flammability 44


Rating (1 – 5) Flammability


characteristics


Pyrophoric, Pyrophoric, Flammable


Flammable


Reactivity (1 – 5) 23 Potential effects


Detonation, Combustion


4


Flammable Corrosive


2 Inhalation Inhalation Skin irritation Odourless Repulsive Odour Odourless Repulsive Sweet Odour 4 Pyrophoric 3


Detonation Combustion


To provide the necessary protection, fixed gas monitoring systems are installed in critical areas throughout the plant; traditionally, these have used paper tape technology, but the high cost paper tape monitors are increasingly being replaced by electrochemical sensors, which offer both cost of ownership and performance advantages. It is estimated that electrochemical hydride detectors now account for around 60% of the market and the trend continues upwards.


During the last twenty years, City Technology has built a worldwide reputation with its state of the art Sensoric range of exotic gas sensors. In particular, the hydride sensors, which are used throughout the world in semiconductor manufacturing plants, make a critical contribution to the operation of the plant and the protection of the facility infrastructure and the safety of the workforce. The Sensoric sensors guarantee the safe manufacture of the technology that underpins the digital world that we take so much for granted today through an outstanding track record for performance, quality and reliability. The Sensoric product attributes, combined with the outstanding service, support and technical backup from City, have made the Sensoric hydride sensors the unit of choice for instrument manufacturers. Sensoric hydride sensors are the undisputed market leader, with a large installed base in this critically important specialised sector.


Decaying


Horseradish Odour


4 Flammable 0 Phosphine PH3


Pest Control 4


Inhalation Diborane B2H6 4 Inhalation


Hydrogen Selenide


H2Se


Semiconductor Semiconductor Semiconductor Semiconductor Semiconductor Photovoltaic


4 Inhalation


Although relatively small compared to semiconductor manufacturing, the carbon-free energy generation sector is another important area that used exotic gas sensing. The volume manufacturing of photovoltaic converters, which generate pollution-free electricity directly from sunlight, is rapidly increasing to meet the demand for clean energy generation. Many new production facilities are coming on- stream, ramping up the need for high reliability safety and monitoring systems to protect people and plant. The latest generation of Sensoric’s hydride sensors, which provide significantly improved performance over the generation they replace, are already playing a critical part in supporting this essential new industry.


To meet users’ requirements for longer operating life, increased responsiveness and greater stability in the high flow, high temperature environment in which they are typically used, the new generation of hydride gas sensors utilise innovative ionic liquid electrolyte to provide outstanding performance. Hydride gas sensors and detectors must exhibit high stability throughout the equipment’s working life and function effectively in continuous sample flow and high temperature conditions. The consequences of false alarms and process downtime are very costly in continuous manufacturing processes such as wafer fabrication, and manufacturers have constantly sought the most reliable instrumentation to protect their product integrity, facilities and employees.


The new designs are enhanced versions of existing arsine, silane and phosphine sensors with an ionic liquid electrolyte in place of the original gel; two new sensors that are characterised to diborane and hydrogen selenide are also introduced.


Ionic Liquids


Ionic liquids are salts that are liquid over a wide temperature range, including room temperature, and typically contain at least one organic ion. They have been known for over a century, but only in the last decade have their superior qualities been appreciated and used in material applications. The patented ionic liquid combination possesses excellent thermal stability and no measurable vapour pressure. The


AET


April/May 2010


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