TDDB improvement by optimized processes on metal–insulator–silicon capacitors with atomic layer deposition of Al2O3and multi layers of TiN film structure

A metal–insulator–silicon (MIS) capacitor with hemi-spherical grained poly atomic layer deposition (ALD) deposited Al2O3 and multi-layered chemical vapor deposition (CVD) TiN structure is fabricated. The impact of the deposition process and post treatment condition on the MIS capacitor's time-dependent dielectric breakdown (TDDB) performance is also studied. With an optimized process, it is confirmed by Auger electron spectroscopy and secondary ion mass spectrometry analysis that the Al(CH3)3/O3-based ALD Al2O3 dielectric film is carbon free and the hydrogen content is as low as 9 × 1019 cm−3. The top electrode TiN is obtained by multi-layered TiCl4/NH3 CVD deposited TiN followed by 120 s post NH3 treatment after each layer. This has higher diffusion barrier in preventing impurity diffusion through TiN into the Al2O3 dielectric due to its smaller grain size. As shown in energy dispersive X-ray analysis, there is no chlorine residue in the MIS capacitor structure. The leakage current of the capacitor is lower than 1 × 10−12 A/cm2. No early failures under stress conditions are found in its TDDB test. The novel MIS capacitor is proven to have excellent reliability for advanced DRAM technology.