A theoretical model of production and relaxation of stress in ion-implanted silicon is proposed. It is based on the assumptions that the point defects are the source of mechanical stress and that the relaxation of stress is due to the viscous flow of ion-irradiated silicon. The integrated stress acting in a damaged layer has been studied as a function of the -ion current density j = 0.01-, ion energy -160 keV, substrate temperature T = 78-500 K and dose in the range up to . It was shown that the maximum integral stress values induced in silicon are of the order of 100 N . The maximum is reached at a dose of about that corresponds to the silicon-amorphization dose. Stress due to implanted ions is essential for the high-dose region and it dominates at high temperatures of the substrate.

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The model of amorphization of crystals induced by ion irradiation is considered. The model describes two stages of the amorphization, the generation of primary defects by collision cascades and the collapse of crystalline regions, which begins when the concentration of the primary defects reaches about 10%. Due to the colapse of crystalline regions, the total defect concentration increases up to about 80% for rather small increment of the fluence Φ. The defect concentration and the integral stress were calculated theoretically for the silicon samples subjected to irradiation with light, average, and heavy mass ions. The integral stress was analysed as the sum S = S d + Sion, where the S d and Sion terms correspond to the stresses due to point defects and implanted ions, respectively. At low fluences, Φ < Φa (where Φa is the characteristic amorphization fluence), the term S d linearly depends on the fluence and essentially exceeds the stress due to implanted ions. The integral stress acquires a maximum value at Φ = Φa. At higher fluences, Φ > Φa, the term S d considerably decreases and the Sion term dominates the integral stress. In this Φ region, the stress saturates to the constant value, which is larger for the lighter ions and smaller for the heavier ones.

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