The semiconductor industry demands the highest possible purity for its graphite materials, especially for graphite components that come into direct contact with semiconductor materials, such as crucibles and sintering molds. Excessive impurities can contaminate the semiconductor materials. Therefore, not only is the purity of the raw graphite strictly controlled, but it also undergoes high-temperature graphitization to minimize ash content.
The semiconductor industry also requires fine-grained graphite. Fine-grained graphite is not only easier to machine with precision, but also boasts high-temperature strength and minimal wear. Sintering molds, in particular, require extremely high machining precision. Because graphite components used in the semiconductor industry (including heaters and sintering molds) must withstand repeated heating and cooling cycles, the graphite material must exhibit excellent dimensional stability and thermal shock resistance at high temperatures to maximize their lifespan. Graphite made from uncalcined petroleum coke is a fine-grained material with high mechanical strength. It can be used in electronic products such as crucibles, thin plates, disks, heaters for vacuum and high-frequency furnaces, heat shields, graphite dishes for melting pure metals, grippers (chucks) for high-temperature experimental equipment, hot-pressing dies, and filters. This material can operate at temperatures below 2500°C in inert or protective atmospheres.
Ultra-pure, high-strength graphite with a protective layer is made from ordinary fine-grained graphite that has been purified and degassed in a vacuum, followed by surface densification with pyrolytic carbon. These products (heaters, disks, graphite dishes, etc.) can be used to grow silicon thin films using the gas epitaxial growth method. The thickness of the densified protective layer formed by the pyrolytic carbon is no more than 2 mm. A thin layer of pyrolytic graphite up to 0.1 mm thick can also be deposited on the surface of the densified product.