Novel energy-filtered implantation technique for field stop formation in silicon power devices

Abstract

Insulated Gate Bipolar Transistors (IGBTs) power devices require high blocking capability, low on-resistance as well as adaptable switching behaviour. The technique presented in this work aims to realize continuous deep ($>40\mu m$) n-type profiles as field stop structures in high voltage silicon IGBTs (1200 V) to adjust the switching capability. Hydrogen-related donor (HD) defect complexes perform as n-type dopants in single crystalline silicon. Up to now, these IGBT field stop profiles are generated using multiple high energy (up to $2\mathrm{MeV}$) implantation steps. In contrast, we achieve continuous deep HD profiles in a single implantation step by inserting a micro-patterned silicon membrane (energy filter) into the primary ion beam at an energy of $2.5\mathrm{MeV}$ to provide a beam with a broad customized energy distribution. In this work, we investigate how filter structure, implanted fluence $\Phi$ (from $10^{13}$ cm⁻² to $5\times 10^{15}$ cm⁻²) and annealing conditions affect the depth distribution of HD defect complexes. We found that the electrically active dose divided by the implanted fluence before the energy filter, depends on the pattern type of the membrane (long grooves or squares), the implanted fluence and the annealing hold temperature ($320{}^{\circ }$C to $420{}^{\circ }$C).