Significant Off-State Leakage Reduction for n-FinFET by Self-Adaptive TiN Etching

In this work, the OFF-state leakage (
${I}_{ \mathrm{\scriptscriptstyle OFF}}$
) of short channel (SC) n-FinFETs is revealed to be significantly reduced by the self-adaptive etching of work function (WF) metal TiN. The microloading effect in etch process is employed to realize the self-adaptive etching, which results in a thicker TiN layer with a higher WF on the fin bottom and a thinner TiN layer with a lower WF on the fin top for SC n-FinFETs. No influence is observed for long channel (LC) n-FinFETs, which show the uniform etching of TiN. Such a nonuniform WF distribution can effectively reduce threshold voltage (
${V}_{\text {t}}$
) roll-off for SC n-FinFETs. The TCAD simulation results indicate the enhanced gate-to-channel control induced by the nonuniform WF distribution. It is experimentally demonstrated that ~28% reduction of
${I}_{ \mathrm{\scriptscriptstyle OFF}}$
can then be obtained for SC n-FinFETs using such a low-cost self-adaptive etching process.