Dopant Diffusion-Induced Dielectric Breakdown: Stacked Dielectric Reliability on Heavily Doped Polysilicon

This study identifies a novel failure mode in silicon dioxide/silicon nitride (SiO₂/Si₃N₄) capacitors caused by dopant diffusion in heavily doped polysilicon substrates. Under identical thermal oxidation conditions, the interfacial oxide layer is significantly thinner on p type polysilicon compared to n type polysilicon. N type capacitors exhibit superior performance, with a breakdown voltage of 88 V, whereas p type capacitors demonstrate lower breakdown voltage of 51 V. The time-dependent dielectric breakdown (TDDB) analysis indicates that n type capacitors exhibit lifetimes exceeding 10 years under high-voltage stress at 125 °C. In contrast, p type capacitors demonstrate rapid failure when subjected to a voltage of 30 V. Conduction analysis reveals that Poole–Frenkel conduction dominates the stacked dielectric layers, but thinning of the interfacial oxide layer significantly increases Fowler–Nordheim tunneling, ultimately driving stacked dielectric breakdown. These findings highlight the critical role of dopant diffusion in interfacial oxide reliability and provide insights for improving the performance of high-k stacked dielectrics in heavily doped polysilicon.