Plasma-Assisted ALD TiN/Al2O3 stacks for MIMIM Trench Capacitor Applications

In this paper we report on the overall plasma-assisted ALD processes of Al2O3 and TiN conducted in a single reactor chamber and at a single temperature (340 oC). The individual Al2O3 and TiN films in the stack were consecutively deposited in such a way that they were separated by purge intervals ranging from 15 to 300 s. Time-resolved mass spectrometry, TOF-SIMS depth profiles and C-V measurements of the deposited stacks show practically no evidence of precursor cross-contamination by the individual TiN and Al2O3 deposition steps. Based on these results and previous work on planar plasma-assisted ALD TiN/Al2O3/Si MOS capacitor structures, the way was paved to deposit a TiN/Al2O3/TiN/Al2O3 stack on high aspect ratio (~ 17) structures in silicon. Step coverages of at least ~ 90 % and ~ 40 % are consistently obtained for the deposited Al2O3 and TiN layers, respectively. The trench capacitors demonstrated leakage current densities of 10-8 – 10-7 A/cm2, a capacitance density of 180 nF/mm2 and dielectric breakdown field values of 6 – 9 MV/cm