Preparation method for highly-doped phosphorosilicate glass film

The invention discloses a preparation method for a highly-doped phosphorosilicate glass film. The preparation method includes the following steps: forming a gate oxide layer, a polycrystalline silicon gate and a side wall on a silicon substrate; injecting a drain source and carrying out rapid thermal annealing; depositing an SACAD PSG (Selected Area Chemical Vapor Deposition Phosphosilicate Glass) film; depositing an HDP PSG (High Density Polyethylene Phosphosilicate Glass) film; and etching a contact hole. According to the preparation method, the phenomenon that the silicon substrate is damaged by over etching of the contact hole can be avoided; and the PSG film prepared by the method has excellent hole-filling performance and a film structure easy to etch. During preparation, firstly, a layer of PSG film is grown by using an SACAD deposition process; and secondly, a highly-doped PSG film is grown by using an HDP CAD deposition process. Due to the utilization of the characteristic that the SACAD PSG film is uniform in the phosphor doping mount, the position of a starting point at the bottom of the HDP PSG film flower-shaped casing is heightened, a process window for selective etching of the contact hole is increased and further the phenomenon that the silicon substrate is damaged caused by the over etching of the contact hole and the performances of the devices are effectively maintained.