Reducing breakthrough dislocation toward Si/SiGe heterostructure to improve advanced HKMG SRAM device performance by optimizing fluorine co-implantation

This paper studies how boron thermal diffusion in SiGe heterostructure are influenced by different source drain extension high-energy fluorine implant after SiGe thermal process for advanced HKMG SRAM device. Different fluorine profiles may introduce different fluorine concentration along Si/SiGe interface and result in fluorine interstitial cluster at different SiGe positions after SiGe 700°C thermal process. Blanket wafer secondary ion mass spectroscopy (SIMS) profiles were compared for different implant schemes and transmission electron microscopy (TEM) micrographs to establish the conditions under which F high energy implant suppresses B diffusion and cause breakthough dislocation at the bottom of SiGe. By tuning F co-implant from high energy into low energy, the breakthrough dislocations at the bottom of SiGe can be eliminated due to less clusters were formed. From real HKMG SRAM p-MOSFET device learning, better junction leakage improvement was found by Flow energy co-implant due to the elimination of cluster-induced dislocations. Ion/Ioff performance enhancement can also be found by suppresing boron transient enhanced diffusion (TED) from in-situ boron doped SiGe. Possible germanium concentration change inside SiGe with different boron diffusion mechanism by different fluorine co-implants may also influence the strain inside SiGe heterostructure and result in electrical device performance.