Resistance increase in CoSi₂ layer by irradiation induced damage

Damage induced by ion irradiation in CoSi₂ layers on SiO₂ films has been investigated. CoSi₂ layers with 25 nm thickness were irradiation with 25 keV Ar⁺ ions to a dose of 2×10¹⁴ cm^-2 with various dose rate. Pulsed irradiation with various duty ratios was also employed. After the irradiation, the change in sheet resistance of the layers was evaluated. The increase in the resistance increased with increasing the dose rate for samples irradiated with dose rates above the critical value of 7.5×10¹¹ cm^-2 s^-1 at room temperature. The increase has been discussed on the basis of our proposed model and attributed to the overlapping of cascade zones induced by irradiation with dose rates above the critical value. The result of the pulsed irradiation showed that the incremental sheet resistance decreases with increasing the irradiation temperature, and the relaxation time was estimated at shorter than 200 μs at room temperature. Higher irradiation temperature and lower dose rate than the critical value result in the lower resistivity CoSi₂ layers.