Eliminating a polysilicon hole defect created during oxide removal

Gate Oxide failure analysis during technology qualification led to discovery of the polysilicon hole defects in large (>;200K μm²) PMOS capacitors. In-line KLA inspections confirmed that polysilicon holes were formed during the salicide block process module. It is hypothesized that a three way interaction between the P+ source/drain implanted boron, heat added during salicide block mask deposition, and NH₄+ in the BOE causes the polysilicon hole. By replacing the BOE (Buffered Oxide Etchant) with a 100:1 HF solution, the creation of polysilicon holes was eliminated as confirmed by KLA and VBD testing.