Ultrapure Refining Methods

Technical Applications


Refining methods which produce ultrapure materials are important for a number of commercial and national defense applications. As feature sizes of integrated circuits get progressively smaller, the purity of the semiconductor materials from which they are fabricated has historically been increasingly important. Development of extremely pure semiconductor crystals is also important for optoelectronic and photonic applications. More recently, chemical vapor deposition and similar thin film techniques have been used to create a pure silicon layer on top of a wafer. That layer is then used to build the actual devices. Consequently, ever increasing the purity of the underlying ingot has become relatively less important to microelectronics. Some processes, such as silicon-on-insulator, even obviate the need for very pure ingots, but the dominant current processes still demand significant purity.


Ultrapure materials are also important for structural applications, since microscopic impurities can cause cracks in ceramics and ceramics-based composites. In general, ultrapure refining methods include micro-gravity and high- pressure fabrication methods which suppress convection currents in the material and allow even distribution of impurities or their elimination.


Internationally, Japan and Germany still lead in the creation of large, pure ingots of semiconductor materials. The ability to create ever larger ingots of pure silicon remains important to advanced microelectronics.