Role of hydrogen anneal in thin gate oxide for multi-metal-layer CMOS process

Influence of hydrogen annealing on NBTI performance

“…It was believed that there is a close link between excessive hydrogen and interface state formation as reported by Lee et al [9]. Si-O bulk defect in the gate oxide is associated with positive charge.…”

“…These process steps include gate oxide thickness change, incorporating fluorine in the gate oxide [7], and oxide nitridation etc [8]. In addition, hydrogen-annealing effect on NBTI in thin gate oxide for Multi-Metal-layer CMOS process is also discussed by Lee et al [9]. Hydrogen or forming gas annealing is often used at the end of the CMOS process in order to passivate the oxide dangling bonds and neutralize the oxide defects [9].…”

“…In addition, hydrogen-annealing effect on NBTI in thin gate oxide for Multi-Metal-layer CMOS process is also discussed by Lee et al [9]. Hydrogen or forming gas annealing is often used at the end of the CMOS process in order to passivate the oxide dangling bonds and neutralize the oxide defects [9]. In this paper, besides annealing at the end of the process, hydrogen annealing after Local Interconnect Layer (LIL) formation and before Contact/Metal is also performed for good device performance, yield and NBTI.…”

Impact of Device Layout and Annealing Process During the Passivation of Interface States in Presence of Silicon Nitride Layers

“…These experimental results on SONOS and MOS devices suggest that the anomalous and the CP data are related to the nitride property to block the hydrogen diffusion [14]- [16] and the impossibility for the hydrogen atoms to pass through the ONO dielectric of SONOS cells (Fig. 8) or through protective nitride caps placed on top of MOS stacks, especially during the final annealing steps at the end of the device processing.…”

“…Manuscript In this framework, this paper reports a deeper analysis with respect to [13] of the anomaly that we discovered in the measured capacitance-voltage ( ) curves of large area SONOS test structures. The impact of the device layout and of the final hydrogen annealing steps on the quality of the Si-SiO interface is analyzed in detail; finally, we trace back these anomalous electrical characteristics to the silicon nitride property to block the diffusion of the hydrogen atoms through the ONO stack [14]- [16], thus resulting in an incomplete passivation of the Si-SiO interface dangling bonds and in a large concentration of surface states. Furthermore, measurements performed on MOS capacitors featuring a protective nitride cap on top of the gate stack confirmed this interpretation [17], [18].…”