Epitaxial ALD BeO: Efficient Oxygen Diffusion Barrier for EOT Scaling and Reliability Improvement

In a previous study, we demonstrated that the BeO film grown by atomic layer deposition (ALD) on Si and III-V metal-oxide-semiconductor devices has excellent electrical and physical characteristics. In this paper, we discuss the physical and electrical properties of ALD BeO as an oxygen diffusion barrier on scaled 4-nm HfO₂/BeO gate stacks. Thin BeO layers are deposited onto (100) p-Si substrates as an alternative to SiO₂ as an interfacial passivation layer (IPL). X-ray photoelectron spec troscopy and transmission electron microscopy show that the BeO IPL acts as an effective oxygen barrier against SiOιι. native oxide formation during postdeposition annealing (PDA). The use of ALD BeO as an oxygen diffusion barrier results in lower equivalent oxide thickness, more competitive leakage current, and better reliability characteristics after PDA than Al₂O₃ and HfO₂ gate stacks.