Anti-ferroelectric Hf_xZr_1-xO₂ Capacitors for High-density 3-D Embedded-DRAM

Abstract

In this paper, a three-dimensional (3-D) deep-trench capacitor using anti-ferroelectric (AFE) Hf <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (HZO) is experimentally demonstrated as a promising option for embedded dynamic random-access memory (eDRAM) by showing (i) a successful 10ns polarization switching for read/write operations, (ii) maximum operating voltage less than 1.8V, (iii) retention much longer than 1ms, and (iv) endurance reaching 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cycles at elevated temperature. Polarization-voltage (P-V) characteristics and endurance behavior in AFE HZO capacitors are explored through both modeling and P-V evolution during field cycling under extensive pulsing schemes. It is shown that (i) defect diffusion driven by depolarization and (ii) partial domain switching play important roles in endurance fatigue. Finally, a vertical stack with multiple HZO capacitors in parallel is demonstrated, showing a 1T- multi-C memory architecture as a viable path toward future ultra-high density eDRAM technology.