Introduction manner of life time killer and production manner null

摘要

PURPOSE:To add heavy metal in low concentration and to enhance the accuracy of controlling a lifetime by employing powder mixed with heavy metal element as a diffusion source. CONSTITUTION:2-500ppm of heavy metal such as iron by mass ratio is mixed in powder made of polycrystalline silicon particles having several tens mum of particle size to form powder 12. Suitable amount of the powder 12 is scattered to adhere to the surface of a silicon substrate 11, several hundreds-several thousands of substrates 11 are so brought into contact to be superposed as to interpose the powder 12 thereamong, and inserted in this state into a diffusing furnace held at 800-900 deg.C. After the insertion, it is heated at a predetermined rising rate, and heat treated at 1200-1300 deg.C for several hours-several tens hours. With the powder 12 as a diffusion source Fe mixed in the powder 12 is diffused in the substrate 11 by the heat treatment. Thus, since the absolute amount of lifetime killer to be introduced into the substrate 11 is limited, heavy metal concentration can be accurately controlled in a range of relatively low concentration.