Chemical-mechanical polishing of dielectric thin films for integrated giant magnetoresistance non-volatile memories

This investigation focuses on the issues in the integration of Giant Magnetoresistance (GMR) memories using chemical-mechanical polishing (CMP). Depending on the relative orientation of current flow to the GMR multilayer film plane, GMR memory can be classified into two modes, current-perpendicular-to-the-plane (CPP) and current-in-the-plane (CIP). In this study, the CPP GMR integrates PECVD silicon nitride CMP patterning and Cu interconnects, while the CIP GMR requires CMP planarization and polishing of IC-compatible dielectrics, namely silicon oxide and/or silicon nitride.;Our results show that colloidal silica-based slurry is a viable starting slurry chemistry for nitride CMP and is proven benign to Cu interconnects. Through proper combination of CMP process parameters and consumables as well as post-CMP cleaning, good planarity and a very smooth polished surface are obtained. Moreover, the CPP GMR transport test results clearly demonstrate that the nitride CMP process, along with Cu benzotriazole surface passivation techniques, can be successfully incorporated into a GMR memory integration scheme, achieving a low value of effective ;An important aspect of CIP GMR integration is to have a well planarized and highly polished dielectric surface for GMR material deposition when these devices are integrated with Si ICs. CMP polishing of both PTEOS oxide and PVD nitride is investigated, with the surface roughness as the primary metric for CMP evaluation. By comparison, PVD nitride CMP polishing can produce an ultra-smooth surface with RMS surface roughness less than 0.2 nm and is a more robust and manufacturable process for CIP GMR. In addition, a chemical cleaning through heated ammonium hydroxide-peroxide mixture is devised to reduce post-CMP defect levels on the planarized PTEOS oxide surface while a mechanical system with highly-porous PVA brushes removes metal contaminants to a level acceptable to microelectronic manufacturing standards.;To elucidate the basic CMP science. LPCVD silicon nitride is analyzed by XPS and FTIR both before and after CMP, demonstrating the salient increase of oxygen content, amine species and silanol groups forming on the nitride surface. Chemical testing of the collected slurry conclusively determines ammonia as one of the nitride reaction products during CMP. Therefore, nitride hydrolysis is proposed as the dominant chemical component, through which the nitride surface is chemically modified and softened, enabling continuous material removal. Moreover, the nitride polish rate can be promoted or suppressed through the modulation of the nitride hydrolysis reaction.