The preparation of polysilicon films on highly boron doped silicon substrates and their effects on Cu out-diffusion

The behavior of copper (Cu) diffusion at different storage temperatures of heavily boron-doped silicon substrates is investigated. The surface Cu concentration of the substrate with quantitative Cu contamination exhibits an initial increase followed by a subsequent decrease upon storage at 25 °C and 85 °C. The surface Cu, originating from the out-diffusion, can be effectively removed through RCA cleaning. The polysilicon film, prepared by low-pressure chemical vapor deposition (LPCVD) on the back of the substrate, exhibits a pronounced inhibitory effect on the out-diffusion of Cu. This phenomenon can be attributed to the effective gettering of Cu by both grain boundaries and disordered grain structures within the polycrystalline silicon film. Additionally, the multilayered structure of the polysilicon film exhibits enhanced gettering capabilities. The enhanced gettering effectiveness achieved by the multilayer polysilicon film can be attributed to an increased number of interfaces between layers.