Low Temperature Thermal Atomic Layer Deposition of Aluminum Nitride Using Hydrazine as the Nitrogen Source

Aluminum nitride (AlN) thin films were grown using thermal atomic layer deposition in the temperature range of 175-350 degrees C. The thin films were deposited using trimethyl aluminum (TMA) and hydrazine (N2H4) as a metal precursor and nitrogen source, respectively. Highly reactive N2H4, compared to its conventionally used counterpart, ammonia (NH3), provides a higher growth per cycle (GPC), which is approximately 2.3 times higher at a deposition temperature of 300 degrees C and, also exhibits a low impurity concentration in as-deposited films. Low temperature AlN films deposited at 225 degrees C with a capping layer had an Al to N composition ratio of 1:1.1, a close to ideal composition ratio, with a low oxygen content (7.5%) while exhibiting a GPC of 0.16 nm/cycle. We suggest that N(2)H(4)as a replacement for NH(3)is a good alternative due to its stringent thermal budget.