The invention provides a method for injecting
arsenic ions into
polycrystalline silicon, which is characterized in that when
arsenic ions are injected into a
polycrystalline silicon layer, a step of injecting carbon ions is added, when carbon atoms enter the
polycrystalline silicon layer, the carbon atoms replace
silicon atoms to form carbon-
silicon bonds, and because the
radius of the carbon atoms is smaller than the
radius of the
silicon atoms and the
radius of the
arsenic atoms, the distance between lattice point locations is reduced; silicon-silicon bonds around arsenic atoms are replaced by carbon-silicon bonds, the
bond length of the carbon-silicon bonds is small, surrounding
crystal lattices are contracted and distorted, migration vacancies of the arsenic atoms are reduced, arsenic ions with large atomic radiuses cannot pass through the carbon-silicon bonds, meanwhile, the
bond energy of the carbon-silicon bonds is larger than that of the silicon-silicon bonds, the potential barrier of arsenic
ion vacancy migration is further increased, and the arsenic ions with large atomic radiuses cannot pass through the carbon-silicon bonds. The difficulty of arsenic
ion vacancy migration is improved, and finally
diffusion of arsenic ions in the silicon material is effectively reduced; and moreover, the body for
ion implantation is polycrystalline silicon, and the
crystal orientations of the polycrystalline silicon are different in all directions, so that the arsenic ions can generate an equivalent
diffusion inhibition effect in all directions in the polycrystalline silicon.