Metalorganics
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Metalorganics are also known as Organometallics or Metallo-Organics or Organo-Inorganics, and are used extensively in Metalorganic vapour phase epitaxy (MOVPE) of compound semiconductors and Atomic Layer Deposition (ALD) in silicon-based semiconductors.
Metalorganics can be defined as the compounds involving a bonding interaction (covalent or ionic, localized or delocalized) between one or more carbon atoms of an organic moiety and a metal atom or atoms (of main group, lanthanides, actinides, or transition elements). It is worthwhile to note that this definition also encompasses the organic compounds of the metalloids (such as B, Si, Ge, As and Te). Certain metal-containing organic compounds that do not contain metal-carbon bonds are also considered as metalorganics - provided they closely simulate the metalorganic compounds by definition, e.g. the class of metal hydrides, metal alkoxides, metal thiolates, metal amides and metal phosphides.
Ultrapure Metalorganics are sources for optoelectronic and microelectronic applications (e.g. MOCVD and ALD), with highest purity of the order of 99.9999% ("six nines") or greater. These ultrapure metalorganic sources are manufactured by using specially developed innovative synthetic routes, and as such are lowest in particles and deleterious impurities (e.g. metallic, organic and oxygenated etc) at the levels below parts per billion (ppb) and frequently reaching a part per trillion (ppt) level.
[edit] Vapor Pressures of Metalorganics
The vapour pressure of a metalorganic precursor is a crucial parameter that is used to govern the precise concentrations of metalorganic precursors entering the reactor, and subsequently the rate of deposition in MOVPE process. Hence knowing the vapour pressures most accurately is vital to the MOVPE process and the semiconductor growers. The vapour pressures of MOVPE sources at various temperatures can be found out by using an innovative tool, Interactive Vapor Pressure Chart, offered at the website of Rohm and Haas Electronic Materials LLC. Additionally, the techniques for measurement of vapour pressures of Trimetylindium (TMI) with great precision and its accurate vapour pressure equation are discussed in the paper on Vapour pressure equation for TMI from Journal of Crystal Growth(ICMOVPE-XI Proceedings Issue, 2003).
[edit] Environment, Health and Safety Aspects
As MOVPE has become well-established production technology, there are equally growing concerns associated with its bearing on personnel and community safety, environmental impact and maximum quantities of hazardous materials (such as gases and metalorganics) permissible in the device fabrication operations. The safety as well as responsible environmental care have become major factors of paramount importance in the MOVPE-based crystal growth of compound semiconductors.
The article entitled Environment, Health and Safety aspects of Metalorganic Sources used in MOVPE of Compound Semiconductors, (by Shenai-Khatkhate et al, Journal of Crystal Growth, 272 (2004) 816-821), provides the workplace exposure monitoring studies on routinely used MOVPE sources such as trimethylgallium, triethylgallium, trimethylindium, trimethylantimony, dimethylzinc and diethylzinc. Also reviewed in this article are the environmental, health and safety hazard aspects for metalorganics of 15 elements, their decomposition mechanisms, and the means to mitigate and minimize the risks (i.e., engineering controls) involved while using the MOVPE sources, which comprise alkyls or hydrides of aluminum, gallium, indium, nitrogen, phosphorous, arsenic, antimony, bismuth, zinc, cadmium, selenium, tellurium, magnesium, silicon and germanium.
