Structural and electrical properties of CuAlMo thin films prepared by magnetron sputtering

Abstract

The structural and electrical properties of a low resistivity CuAlMo thin film resistor material were investigated. The thin films were grown on Al2O3 and glass substrates by direct current (dc) magnetron sputtering. The key electrical properties of sheet resistance, temperature coefficient of resistance (TCR) and resistance stability were investigated as a function of sputtering pressure and post-deposition heat treatment time and temperature. A low sputtering pressure range of 0.13 to 0.40Pa produced CuAlMo films with sheet resistance in the range 0.1 to 0.2Ω/□ and resistance stability of 0.45 to 0.65% with a TCR of −90ppm/°C which could be shifted to zero following annealing in air at 425°C. Films grown at higher sputtering pressures of 0.53 to 0.80Pa had increased sheet resistance in the range 0.4 to 0.6Ω/□ and inferior stability of 0.8 to 1.7% with a more negative TCR of −110 to −180ppm/°C which could not be shifted to zero following annealing. The stability of the films grown at 0.13 and 0.40Pa could be further improved to <0.25% with heat treatment, due to the formation of a protective aluminium oxide layer. A minimum dwell time of 3h at 425°C was required to stabilise the films and set the electrical properties.