Silicide Applications In Microelectronics

The advent of very-large-scale integration in microelectronics has been achieved by reduction in lithographic dimensions coupled with a corresponding decrease in vertical dimensions in properly scaled device structures. This development has placed severe demands upon interconnection technology. The practice of using semiconducting regions (diffusions or polycrystalline silicon) for interconnecting devices is no longer viable because of the high resistance associated with such regions (i.e. interconnections do not “scale” properly). One solution to this problem is the use of multilevel metallization, but this requires tens of thousands of small contacts to shallow diffusions. Refractory metals such as titanium are being explored as materials which provide the necessary stable low resistance contacts suitable for integrated circuit applications. Another solution to the problem is to develop a higher conductivity material to replace or supplement polycrystalline silicon. Refractory metal disilicides have been extensively investigated for this application -both as a direct replacement for polycrystalline silicon or in a silicide/polycrystalline silicon composite (polycide). A critical review of the present status in both these areas will be presented. Emphasis will be upon our experience gained in conjunction with the development of a 1 μm silicon gate metal/oxide/ semiconductor field effect transistor technology.