A study of 28nm back end of line (BEOL) Cu/Ultra-low-k time dependent dielectric breakdown (TDDB) dependence on key processes

As the device size shrinks beyond 45nm technology node, logic BEOL (back end of line) started adopting Cu/Ultra low k (ULK) to reduce RC delay. With the introduction of low k material, IMD TDDB is notably degraded as numerous publications reported. The impact of ULK material deposition process, barrier layer deposition process on TDDB performance were investigated and discussed in-depth in this paper. In ULK material deposition process, the flow rate of Si-O and hydrocarbon containing precursors and RF power parameters significantly impact RC delay and TDDB performance. Barrier layer thickness, DC power and AC power parameters impact TDDB performance in barrier deposition process. In addition, one simple method of comparison and prediction of IMD TDDB is proposed through the analysis of leakage current and breakdown voltage (Vbd).