Various types of processes for solar grade silicon (SOG-Si) production/purification have been developed with the aim of overcoming the low productivity of the Siemens process These processes can be divided into three groups decomposition and/or hydrogen reduction of plane gases by improving the currently used commercial processes purification of metallurgical grade silicon using metallurgical purification methods and metallothermic reduction of silicon halides by metal reductants such as zinc and aluminum This. paper reviews the features of various SOG-Si production processes particularly the processes based on metallo thermic reduction by classifying them according to the types of reductants and the silicon compounds used Prospects for development of new processes for producing high purity silicon are presented