Exploring FeFET Degradation Mechanisms: Mid-Interlayer as a Viable Solution for Stable Retention, Disturb Immunity, and Low V_th Variation

This study experimentally investigates the unexplored dynamics of retention loss, disturbance, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\text{th}}$</tex> instability in MIFIS FeFETs, featuring a metal-gate interlayer (G.IL)-ferroelectric (FE)-channel interlayer (Ch.IL)-Si stack. To prevent undesired decoupling of polarization <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(P)$</tex> and trapped charges during performance degradation, a mid-interlayer (mid-IL) within the FE layer is proposed. The optimized mid-IL (i) stabilizes the FE phase in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\overline{\mathrm{H}}\text{fZrO}_{\mathrm{x}}$</tex> (HZO) film, (ii) acts as an energy barrier in the gate stack to suppress trapped charge loss toward the channel, and (iii) mitigates channel percolation issues caused by the polymorphic and polycrystalline nature of FE films. These improvements enable an advanced gate stack design with reduced operation voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(V_{\text{PGM}}/V_{\text{ERS}}:17/$</tex> - 14 V), a wide memory window (MW: 10.5 V), stable TLC retention (F <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Delta \text{MW}\sim-6$</tex> % after 10 years at 85°C), disturb immunity <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta V_{\text{th}}=0$</tex> after 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> cycles at 12 V), and low <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{th}}$</tex> variation (54% <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Delta V_{i\mathrm{h}}$</tex> reduction).