End station and beam line design considerations for photoresist outgassing with high energy (MeV) ion implantation

Recently, high energy (MeV) implantation processes have been adopted in mass production semiconductor manufacturing, typically to form deep retrograde wells. Also, triple wells (>2.5 MeV P) and epi-avoidance Buried Implanted Layer for Lateral Isolation (BILLI) implants (>2.0 MeV B) have increased significantly. Although the typical dose of the applications is less than 3E13/cm² and the typical beam current is less than a few hundred particle micro-amperes, special attention needs to be paid to photoresist outgassing during high energy implantation because the range of the dopant is much deeper (resulting in dramatically more outgassing) and collisional interactions between incident ions and residual gases are more complicated than those of high and medium current applications. For low energy implants, neutralization is dominant. This is not necessarily the case for higher energy implants. This paper describes the design considerations for an end station and beam line for photoresist outgas control, especially for MeV ion implantation