5.2 INTRODUCTION

The reactions of Ni and Si for possible use in microelectronic manufacturing have been extensively studied starting in the mid1970s [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. Multiple studies followed that further determined the electrical and mechanical properties of Ni silicide phases, the mechanisms for their formation in thinner films and its dependence on various impurities [1, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52]. Recently, the interest in the low resistivity NiSi increased significantly because of the projected near-term use as contact to the source, drain and gates of CMOS devices. Recent publications from microelectronic companies on NiSi contacts [53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68] point out again that the practical advantages of this material reside in a low thermal budget for formation, a low resistivity in narrow dimensions and a low device leakage. While these device data have shown the feasibility of a NiSi process, the actual use of this new material depends to a great extent on the performance and limitations of the current CoSi ₂ contacts as well as on improvements in yield for the NiSi process. As many properties of NiSi are very different from those of its CoSi ₂ counterpart, a good understanding...