The LPCVD Polysilicon Phosphorus Doped In Situ as an Industrial Process

The growth of phosphorus‐doped in situ polysilicon by low pressure CVD is presented as well as the deposition parameters. The doping source, PH 3 , is diluted in N 2 or Ar. The deposition rate is greater for the N 2 dilution (with the same PH 3 flow rate) and the surface roughness and the grain size are found to depend on the deposition rate which depends on the PH 3 flow rate. It is possible to deposit doped polysilicon onto 3 in. substrates, up to 80 wafers simultaneously, with 2% thickness uniformity and a ± 2 Ω / □ sheet resistivity deviation within the same wafer and better than 6% thickness uniformity and a ± 5 Ω / □ sheet resistivity deviation from wafer to wafer ( R □ Avg ‐ ∼ 30 Ω ) . The film texture preference is <110> in the undoped and <211> in the doped case. It was observed that after annealing at 950°C, 30 min, these textures may change. It was found that the deposition rate depends on the position along the furnace and on the PH 3 flow rate. On the other side, the deposition homogeneity depends on the boat carrier shape.