Formation of vertical links in standard CMOS double-level metallizations by application of Nd:YAG- and excimer-laser radiation

Laser processing of vertical links has been studied on three different layer sequences with main emphasis on statistics. Experiments were carried out with a Nd:YAG and an excimer laser using a fixed number of pulses adapted to the layer sequence. Laser antifuses of different design and sizes were fabricated. Simple expanded interconnections of dimensions 10×10 μm² (10²), 14² and 20² (sequence 1 and 2) and 9.6², 12.6² and 19.5² (sequence 3) turned out to be best suitable. Applying two Nd:YAG pulses, maximum yield of 100% was obtained from 14² and 20²-structures with low mean resistances R_m of 0.18 and 0.104 Ω, and a standard deviation σ_R of 0.145 and 0.06 Ω respectively. Yield obtained from 19.5² was 100% with R_m=0.219, and σ_R =0.199 Ω using 3 pulses and two contacts per structure. By application of two excimer pulses, maximum yield of sequence 2 was 100% obtained from 14²- and 20²-structures with R_m =0.125 Ω and 0.163 Ω and a σ_R of 0.095 and 0.12 Ω respectively. Application of three excimer pulses on 12.6²-structures lead to a yield of 99.6% with R_m =0.552 and σ_R=0.357 Ω. In all yield evaluations, resistances ⩾3 Ω were treated as a failure