Study on polysilicon resistivity control with nano-scale grain size

Resistivity of boron-doped polycrystalline-silicon (polysilicon) film was investigated experimentally with wide range of doping concentration (5×10¹⁸~1.4×10²⁰cm^-3) and various annealing conditions (950~1050°C, 10-30mins), which results in sheet resistance of 89.5~149000Ω/°C and resistivity of 2.6×10^-3~4.3Ω·cm. Mathematical fitting curve shows perfect consistency of resistivity as function of average dopant concentration lower than 8.5×10¹⁹cm^-3. While at higher concentration where sheet resistance is lower than 170Ω/°C, it is verified that dependence of resistivity of annealing temperature can be represented by the average nano-scale grain size. The average diameter of heavily doped (1.4×10²⁰cm^-3) polysilicon is 85nm, 99nm and 111nm at 950°C, 1000°C, 1050°C, respectively. Combining curve-fit and annealing temperature, resistivity of polysilicon thin film can be precisely controlled with an error less than 10%. The resistivity changes with nano-scale grain size are discussed.