Vt Fine-Tuning in Multi-Vt Gate-All-Around Nanosheet nFETs Using Rare-Earth Oxide-Based Dipole-First Gate Stack Compatible with CFET Integration

This work demonstrates a dipole-induced $\mathrm{V}_{\mathrm{t}}$ fine-tuning on scaled Gate-All-Around (GAA) nanosheet (NS) nFETs (48 nm CPP, 16 nm $\mathrm{L}_{\mathrm{g}}$). Thanks to a novel Rare-Earth-Oxide (REO) as a moderate n-type dipole former, $\sim 50$ mV-step $\mathrm{V}_{\mathrm{t}}$ modulation is demonstrated even in a drive-in-free dipole-first integration scheme. $\mathrm{V}_{\mathrm{t}}$ shift-dependent slight mobility degradation is seen on long-channel planar RMG nFETs, however, improved $\mathrm{D}_{\text{it}}$ and PBTI max. $\mathrm{V}_{\text{ov}}$ confirmed the high-quality gate stack. On the scaled NS nFETs, REO dipole-first demonstrates a gradual $\mathrm{V}_{\mathrm{t}}$ modulation with maintained $\mathrm{V}_{\mathrm{t}}$ variability and device performance while outperforming LaO dipole-first and dipole-last multi $-\mathrm{V}_{\mathrm{t}}$ options.