Study On The Process Technology Of P-Type Epitaxial Silicon Wafer

In the 21st century, silicon will still be the mainstream of microelectronics. Silicon epitaxial material has provided solid and reliable material base for semiconductor silicon devices,especially all kinds of silicon integrated circuits,and supported the sustainable development of contemporary microelectronic industry. Meanwhile the manufacture level of epitaxial material becomes an important symbol to measure the independence of the IC industry in the world.P/P+ epitaxial silicon wafers are mainly applied in very large scale IC and power devices, and are getting much more attention. However, with the increasing of wafer's diameter, it is more and more difficult to control the uniformity of the thickness and resitivity of P/P+ epitaxial wafer. Process optimization to improve electric parameters of epitaxial layer is one of the challenges of device manufacture.The growing principle and process of the epitaxy are analysed in this paper, and the critical factors which affect the growing rate and quality of epitaxy are also studied. The relationship between the silicon epitaxial growth rate and the flow rate of silicon source, the flow rate of hydrogen carrier gas as well as the growth temperature was also studied systematically. It is found the asymmetry of thermal field is the important factor of affecting the uniformity of P/P+ silicon epitaxial wafer's thickness. By the method of temperature compensation, the influence of asymmetry of thermal field has been suppressed, as a result, the uniformity of P/P+ silicon epitaxial wafer's thickness has been improved and can be controlled within 1%.The outward diffusion in solid state and self-doping phenomenon of impurities in substrate is the important reason of poor uniformity of P/P+ silicon epitaxial wafer's resitivity. Self-doping phenomenon has been effectively suppressed by using two-step epitaxial growth mode, the uinformity of P/P+ silicon epitaxial wafer's resistivity has been improved and can be controlled within 2.5%.The relation among intrinsic thickness and the resistivity and thickness of the epitaxial layer has been found during two-step epitaxial growth mode, and their varying trend has also been confirmed by experiments.