Lanthanum doped hafnium oxide thin films deposited on a lateral high aspect ratio structure using atomic layer deposition: A comparative study of surface composition and uniformity using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry

Hafnium oxide (HfO₂) thin films doped with lanthanum (La) can achieve ferroelectricity, making the material applicable in transistor and memory technologies. To downscale future devices in the semiconductor industry, the application of the doped HfO₂ material requires deposition on complex microscopic three-dimensional (3D) structures. A widely used process for the preparation of doped HfO₂ thin films is atomic layer deposition (ALD). With 3D geometries, it is challenging to deposit materials homogeneously and to effectively characterize them. To forego the difficulties in film characterization, two-dimensional (2D) PillarHall lateral high aspect ratio (LHAR) test structures are used. These structures expose a lateral surface to facilitate the conformality analysis of thin films deposited using two different ALD processes. In this work, we aim to further advance the arsenal of analysis techniques used to characterize La doped HfO₂ thin films by using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze uniformity and composition. The XPS technique can be applied and established as a method for the optimal analysis of thin films deposited on LHAR structures. Both techniques provide a complementary analysis of material formation, elemental distribution, measurement along the LHAR depth range, and can probe differences between deposition processes.