Investigation of In-Situ Boron-Doped Epitaxial Si1-xGex/Si Films for Three-Dimensional Dynamic Random Memory (3D DRAM) Applications

To investigate the impact of in situ boron (B) doping on epitaxial Si 1-x Ge x or Si films, six sets of samples with controlled Ge composition and B concentration were synthesized on p-type Si substrates via reduced-pressure chemical vapor deposition (RPCVD). The resulting films were systematically characterized using high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), and high-resolution transmission electron microscopy (HRTEM). For the SiGe:B single-layer samples, SIMS and AFM results demonstrate that increasing the B doping concentration effectively achieves strain compensation in the SiGe films but simultaneously degrades the surface quality, as evidenced by an increase in the root mean square (RMS) surface roughness. For the SiGe/Si:B superlattice samples, HRXRD and HRTEM images reveal epitaxial film has high-quality crystal structure, no observable dislocations. HRXRD analysis reveals that the epitaxial SiGe/Si:B superlattice sample is fully strained and exhibits a high-quality crystal structure. HRTEM images reveal no observable dislocations. Energy-dispersive X-ray spectroscopy (EDS) analysis suggests that the interfacial transition width is broadened to approximately 4.4 nm, which is attributed to B-induced Ge segregation. The superlattice film exhibits an RMS roughness of 0.29 nm and a Hall mobility of 160 cm 2 ·V -1 ·s -1 . These analyses demonstrate that in situ B doping in epitaxial Si 1-x Ge x or Si films enables the realization of high-quality, fully strained SiGe/Si superlattices with sharp interfaces and low surface roughness. These properties exhibit material properties consistent with the requirements for application as channel materials, as well as source and drain components, in three-dimensional dynamic random-access memory (3D DRAM) transistors.