Application of MoSi2to the double-level interconnections of I2L circuits

A new MoSi
2
-CVD-Al double-level interconnection system is developed to obtain a high packing density in I
²
L circuits. Taking advantage of MoSi
2
, a fine pattern consisting of a linewidth of 2.5 µm and a spacing of 1 µm is achieved for the first-level interconnections. This new system has a higher reliability than the normal Al-CVD-Al structure because of the stability of the MoSi
2
surface. The fundamental properties of I
²
L gates with MoSi
2
interconnections, namely, gain, propagation delay time, and toggle frequency of a T flip-flop, are measured. At practical injector currents, they show nearly the same values as with Al interconnections. The resistance effects of MoSi
2
interconnections are calculated with regard to the unbalance of the injector currents and increase of the propagation delay time. The calculations show that these effects can be ignored at an injector current of 1 µA/gate. At higher injector currents, the MoSi
2
interconnection resistance must be taken into account in I
²
L pattern layout.