Radiation hardening method for shallow trench isolation in CMOS

A radiation-hardened STI process includes implanting a partially formed wafer with a fairly large dose (10¹³ to 10¹⁷ ions/cm²) of a large atom group III element, such as B, Al, Ga or In at an energy between about 30 and 500 keV. The implant is followed by an implant of a large group V element, such as P, As, Sb, or Bi using similar doses and energies to the group III element. The group V element compensates the group III element. The combination of the two large atoms decreases the diffusivity of small atoms, such as B, in the implanted areas. Furthermore, the combination of the group III and group V elements in roughly equal proportions creates recombination sites and electron traps in the field oxide, resulting in a radiation hardened semiconductor device.