Information on the technology of polycrystalline silicon obtained by the technology of hydrogen reduction of silicon chloride compounds is given. The focus is on the technology of silicon rods-substrates for the subsequent deposition of silicon on them. The monograph develops a new approach to solving the scientific problem of identifying the causes and developing methods for preventing mechanical destruction of silicon rods during polycrystalline silicon deposition. The analysis of the stress state of the silicon rod, carried out in the framework of the theory of elasticity, showed that the sum of the compression stresses under the weight of the buildup layer of polycrystalline silicon and the thermoelastic stresses arising in the silicon rod during the hydrogen reduction of trichlorosilane is lower than the ultimate strength of silicon, so they themselves do not lead to destruction of the rod. Practical ways to improve the technology to improve the characteristics of the final product are given. For researchers, technologists, faculty, graduate students and undergraduates.