Research On The Key Technology Of CZ Silicon Crystal Growth Furnace

Information industry and green energy industry are the pillar industries of modern world, as the fundamental material of these pillar industries, silicon single crystal is essentially important. Now, most 3-8 inch silicon crystal for IC manufacture in China is pulled by imported CZ furnace. For 90nm-45nm line width IC fabrication, all the process technology, control system and equipments for crystal growth are monopolized by foreign companies. R&D of CZ furnace in China started from the fifties last century, but the accuracy of equipment manufacture is not good enough together with a low level of auto control are the bottle-neck for a long time. These make the domestic CZ furnace cannot meet the requirements of growing silicon crystals for ULSI.In this article, the key technical difficulties of CZ furnace for IC are solved in the first place. The crystal diameter test and auto-control technology of automatic CZ furnace is researched, and for the first time the double CCD diameter control system based on the identification of uncompleted image is advanced. The auto-control technology and interlinking between control loop are developed; process technology as pump down, leak check, pressurization, melting, etc., totally 12 stages and thousands of control parameters are included in this system. The fully auto-control system of CZ furnace is realized for first time in China, and it successfully breaks the foreign monopoly of IC level CZ furnace.The silicon wafer, which is used for ULSI fabrication, is the most advanced information functional material, it directly related to the development of information industry and national security. When growing a 12in silicon crystal, decreasing the COP defects density is the key problem to meet the requirements of 90nm-65nm IC fabrication, for solving this problem a lot of research works were done. Under the direction of COP defects formation theory of V/G (V is the crystal growth rate and G is the axial temperature gradient near the crystal growth interface), two revolutionary improvements on crystal growth control system are made, and they are the diameter control by heater power adjustment and melt level control. By using these new technologies, the density and size of COP defects are decreased thus solved the key problem of growing 12in silicon crystals for USLI.Now, photovoltaic energy is being put forward by legislation in countries like Germany and Spain, green energy and low-carbon life are advocated all over the world and developing very fast. From 2006, thousands of CZ furnaces are assembled in China, and it provides world's 80% productivity of the PV wafers. In order to save the production costs, a high efficiency 22 inch hot zone is developed by changing the heat shield material and by the optimization of heater dimension at the end of this article.The creative points of this article are:1) R&D of the control system for auto-control CZ furnace; 2)With the new technology, the identification of uncompleted image, the double CCD diameter control system is advanced to improve crystal diameter control effects; 3) Diameter control by heater power adjustment together with melt level position control technologies are introduced to decrease COP density and size; 4) Sub heater design is used for hot zone optimization for increasing axial temperature gradient, so as to increase the crystal growth rate and save the production costs.