Suppression of crack formation in wafer-scale amorphous SiNx films by residual hydrogen-ligands manipulation

Abstract

Plasma-Enhanced Chemical Vapor Deposition (PECVD) of amorphous silicon nitride (SiN_x) thin films is a critical procedure in microelectronics serving as a surface passivation layer and dielectric barrier. However, intrinsic film stress continuously builds up along with PECVD growth, leading to film cracking. How to achieve crack-free PECVD amorphous SiN_x film within a large thickness range remains a critical unresolved challenge in semiconductor industry. In this study, we revealed that high residual NH ligands from the NH₃ precursor could induce excessive tensile strain at the SiN_x/Si wafer interface and consequently aggravate SiN_x film crack formation. With a heating pretreatment on the wafer, residual H ligands were effectively reduced to achieve homogenous chemical composition in SiN_x film. As a result, the crack number declined ∼42% and the remaining crack length was substantially shorter in contrast to the original SiN_x film. This work demonstrates the crucial role of residual ligands on internal strain regulation and points out a pathway to achieve crack-free PECVD SiN_x films in industrial manufacturing.