Effects of Ti doping on blister suppression in sputter grown hafnium oxide thin films

In this work, we report a simple and cost-effective strategy to suppress blistering in hafnia (HfO₂)-based thin films deposited by DC magnetron co-sputtering at room temperature. In particular, we report the influence of titanium (Ti) incorporation (HfOₓ:Ti) with focus on the structural, optical, and morphological properties. Rutherford backscattering spectrometry (RBS) reveals Ti contents increasing from 5 to 7 at% by raising the power applied to the Ti cathode. Atomic force microscopy (AFM) and scanning electron microscopy show pronounced blistering in pure HfOₓ films, whereas the introduction of a small Ti fraction alters film compactness and progressively suppresses blister formation. The evolution of blister distribution and its effect on surface roughness are systematically investigated as a function of Ti content by AFM, demonstrating significant morphological changes with only a minor variation in the Ti concentration. X-ray diffraction indicates that Ti doping induces amorphization of the monoclinic HfO₂ phase, shifting the residual stress from compressive to tensile. Such structural transition is strongly correlated with the observed morphological modifications. Regarding optical properties, all samples show an average transmittance of approximately 80 % in the visible range, while the optical band gap decreases with increasing Ti content. In addition, spectroscopic ellipsometry (SE) further confirms the band-gap trend and reveals the tunable optical constants as a function of the Ti level. • A room-temperature method is reported to suppress blistering in HfO x thin films. • Ti doping shifts stress from compressive to tensile, reducing blister formation. • Minimal Ti incorporation (≤ 7 at%) significantly enhances HfO x film integrity. • Improved film compactness and stress uniformity confirmed by SEM and AFM. • Optical band-gap narrows and UV extinction increases with Ti doping.