ALD and Parasitic Growth Characteristics of the Tetrakisethylmethylamino Hafnium (TEMAH)/H[sub 2]O Process

The continuous downscaling of complementary metal oxide semiconductor devices has required the integration of Hf-based high-k materials as gate dielectrics deposited by atomic layer deposition (ALD). When tetrakisethylmethylamino hafnium (TEMAH) is used as the metallic precursor to deposit such Hf-based materials, its limited thermal stability can result in precursor decomposition. This paper shows to what extent precursor decomposition affects the growth behavior of the TEMAH/H 2 O ALD in the temperature range 285-365 °C as well as the properties of the deposited HfO 2 layer. In this temperature range, the TEMAH pulse does not saturate up to pulse lengths of 10 s due to parasitic growth. Parasitic growth occurs when chemisorbed TEMAH ligands decompose and newly introduced precursor molecules react with these decomposed surface sites. The existence of such uncontrolled growth was proven by the repetition of TEMAH/N 2 reaction cycles, resulting in the deposition of a poor-quality Hf-based layer, while its contribution depends on both the reaction temperature and the TEMAH pulse length. Finally, also the H 2 0 pulse needs to be strictly controlled because too long pulses result in temperature-induced dehydroxylation of the surface, lowering the GPC of the TEMAH/H 2 O process with up to ~ 12% at 285°C.