How to characterize hazards in emerging technologies? The GaN epitaxy example.
Proust, Nicole; Poisson, Marie Antoinette ; Picot, Andre
(TRT France (authors 1 and 2) CNRS Gif sur Yvette France (authors 1 and 3))
New semiconductors called "nitrides" and based on AlGaN/GaN/GaInN materials can be used for amber and green emitters for various applications. They are deposited by MOCVD and there is a need for hazards evaluation. Dust and gaseous molecules can be released when the preventive maintenance is done on the MOCVD machine (deposition chamber, pumping group, main maintenance) or when the substrates are unloaded. A bibliographic search has been done on the toxicology of Ga and In compounds. A brief summary of what is known on the toxicity of the various molecules and their effect on the target organs will be presented. Hazards on GaN MOCVD maintenance are under characterization. Epitaxial growth is done in an industrial machine with metalorganics molecules (Ga, In, Al? based) and NH3. Dust from the deposition chamber can be collected. GaN small size particles can be inhaled if dispersed into the atmosphere and interact with all the respiratory tract from the nose to the lung alveoli. If there are not dispersed, they can sediment on the flat surfaces near the machine and lead to an oral exposure. The size, shape and composition have been measured in a scanning electron microscope. Some hazards from the pumping group have been demonstrated during maintenance operation. Al, Ga and In are slightly incorporated in the Fonblin oil, we do not know under which molecular form. Peaks of gaseous ammonia NH3 and hydrogen cyanide HCN (if no sulfur compound interference) have been measured by different methods (electrochemistry, colorimetry?) in air at room temperature over oil after collection. As some hazards have been demonstrated, in order to lower the risk of exposure some modification of work procedure have been proposed to enhance safety at work during maintenance operations.
[abstract as .pdf]