Solid State Synthesis Czochralski Method Bridgman-Stockbarger Technique Zone Melting Method Flame Fusion Method (Verneuil Method)

1. Czochralski Method 2m Crystal Rod Czochralski Puller Melting of raw materials or dopants Seed growth and crystal pulling Cooling 2m Crystal Rod Sliced Si wafer Memory chips on si wafer Czochralski Puller ■ Principle & Process Crystal growth method to obtain semiconductors (e.g. Si, Ge, GaAs) and metals (e.g. Pd, Pt, Ag, Au). ■ Characteristics Rod-shaped single crystal is obtained from a melt of the same composition of melt. Very large crystal is obtained at once. (e.g. 50 kg silicon rod with the size of ~2 m and width of 30 cm) Extremely little impurities. (< 0.01 ppb) Drawback: Materials with high vapor pressure cannot be grown. ■ Usages & Applications Production of highly pure metals, semiconductors, salts, and synthetic gemstones. Mass production of silicon wafer Dopants can be added to make p-type (Boron dopant) or n-type (Phosphorus dopant) semiconductors.

2. Bridgman-Stockbarger Technique Stockbarger method Bridgman Furnace Bridgman method ■ Principle & Process Heating polycrystalline material above its melting point and slowly cooling it from one end of its container, where a seed crystal is located. Stockbarger method: As a pulling method like Czochralski method, boat pulled out through temperature gradient Bridgman method: Melt is inside a temperature gradient furnace ■ Characteristics The shape of the crystal is defined by the container Drawback: Material is constantly in contact with crucible or sample boat, which introduces mechanical stress that possibly changes ideal crystal structures. ■ Usages & Applications Simple and popular way to producing semiconductor crystals such as GaAs, InP, CdTe)

3. Zone Melting (Zone Refining) Method Zone Refining Furnace Heating coil Unmelted region Tantalum crystal (99.999% purity) Tantalum capacitor ■ Principle & Process Method for purifying crystals: Impurities concentrate in the melt, and move to one end of container. Molten zone melts impure solid at its forward edge, and purer material is solidified behind it. ■ Characteristics Pure solid can be obtained in a simple manner. Drawback: Materials with high vapor pressure cannot be grown. ■ Usages & Applications Preparing high purity materials, mainly semiconductors for manufacuturing transistor.

4. Flame Fusion Method (Verneuil method) Verneuil Furnace Gemstones Refined Sapphire Unrefined Ruby Rod ■ Principle & Process Precursor pass through flame and then melted into liquid Melted droplets fall on surface and crystal grows on it. ■ Characteristics Rod-shaped gemstone crystal is obtained. Useful for materials with high melting points. Drawback: Excess oxygen induces gas bubble which induces imperfection of solids. ■ Usages & Applications - Growing crystals of metal oxides with high melting points, such as gemstones (ruby, sapphire, spinels..)