Reduced temperature crystallization of bismuth substituted iron garnet films using oxygen plasma annealing

In this thesis, we are attempting to reduce the thermal budget required to crystallize garnet films (Bi2Dy1Fe4Ga1O12) by using plasma annealing. in order to make this material more compatible with industrial CMOS processing. We have optimized the plasma parameters to obtain the optimal crystallization conditions and optimal magnetooptical characteristics. In addition, the effects of plasma annealing on crystallization and magneto-optical parameters are examined by comparing the plasma annealed garnet samples with traditional rapid thermal and oven annealed garnet samples. The thermal budget required to crystallize Bi2Dy1Fe4Ga1O12 thin films have successfully been reduced to a temperature as low as 515 °C by exposing the films to radio frequency (13.56 MHz) oxygen plasma. The crystallization was achieved at temperature more than 100 °C below the temperatures required for the crystallization via conventional rapid thermal and oven annealing. A conductor (gold foil) attached in thermal contact with the backside of the sample was found to increase the sample temperature and improve garnet crystallization. Optical emission spectroscopy confirmed the presence of substantial quantities of both atomic oxygen (O) and singly ionised atomic oxygen (O+) under the process conditions (rf power: 500-800 Watts, pressure 2-5 Torr) used to achieve crystallization. It was found that the sample temperature was linearly dependent upon the summation of the logs of the magnitude of emission lines of both O+ and O within the plasma, suggesting that heating of the sample was related to free energy of reactions involving these species.