Impact of ALD TiN Capping Layer on Interface Trap and Channel Hot Carrier Reliability of HKMG nMOSFETs

In this letter, the effect of TiN capping layer on interface quality and the channel hot carrier (CHC) reliability of high-k/metal-gate (HKMG) nMOSFET was investigated. Experiments show that the fresh interface trap density was reduced from ${1.83}\times {10}^{{11}}$ to ${7.75}\times {10}^{{10}}$ cm ⁻² for 1.4 and 2.4 nm ALD TiN capping layers, respectively, while the CHC time-to-failure was worsened by 13%. Combining the chemical analysis by secondary ion mass spectroscopy and the characterization of active energy for trap generation, it is found that the extraordinary chlorine introduced by a ALD TiN capping layer deposition could be responsible for the improved fresh interfacial trap but degraded CHC reliability in HKMG nMOSFETs. The mechanism can be explained by the lower binding energy of Si–Cl than Si–H, which results in more interface passivation but easier to be broken by electrical stress. This finding can provide the guide for the optimization of HKMG process.