In order to detach a silicon thin film from a starting substrate by splitting, a step of implanting species within the starting substrate (10) through a free surface is carried out in order to form a weakening layer (13), at least one intermediate step at a temperature of at least 450°C before and/or after an optional securing step for tightly contacting the free surface with a stiffener, and then a detachment step by splitting along the weakening layer. The implantation step comprises implanting boron, helium, and hydrogen in any order at implantation energies such that maximum boron and helium concentrations are obtained substantially at one and the same depth, with a maximum difference of 10 nm, said maximum concentrations being at a shallower level than the maximum hydrogen concentration, and at implantation doses such that the boron dose is at least equal to 5.10
13 B/cm
2 and the total helium and hydrogen dose is at least equal to 10
16 atoms/cm
2 and at most equal to 4.10
16 atoms/cm
2 , preferably at most equal to 3.10
16 atoms/cm
2 .