Interface Reactions during Annealing‐Induced Ferroelectric Phase Formation in Hf _0.5 Zr _0.5 O ₂ Films on HfS ₂ and MoS ₂

Interface reactions during postdeposition annealing (PDA) of Hf 0.5 Zr 0.5 O 2 (HZO) films grown on HfS 2 and MoS 2 crystals by atomic layer deposition are investigated for potential application in future top‐gate ferroelectric transistors. Both the HZO/HfS 2 and HZO/MoS 2 samples experience blistering of the HZO films when annealed for ferroelectric phase formation at temperatures greater than 500 and 600 °C, respectively, for 1 min in an N 2 atmosphere. The different critical PDA temperatures are associated with different onset temperatures for the thermal decomposition of HfS 2 and MoS 2 crystals, which occur because of reactions with oxygen inadvertently introduced into the N 2 annealing atmosphere. In both samples, the S‐ and O‐related byproduct gases delaminate the HZO film, forming blisters and ruptures with increasing PDA temperatures. Because of the formation of solid HfO x films on HfS 2 via the diffusion of ambient oxygen through the HZO film and randomly located blisters, the HZO/HfS 2 sample develops deep and irregularly shaped encroachment defects with an uneven HfS 2 surface. By contrast, owing to the desorption of the volatile oxide phase (e.g., MoO 3 ) produced during the oxidation reaction, the MoS 2 crystal maintains a flat surface through its layer‐by‐layer decomposition as the PDA temperature increases beyond 600 °C.