Fabrication of Ultrathin Ferroelectric Al<sub>0.7</sub>Sc<sub>0.3</sub>N Films under Complementary-Metal-Oxide-Semiconductor Compatible Conditions by using HfN<sub>0.4</sub> Electrode.
basic_science · Level V
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- Record sourced from PubMed, PMID 39535445.
- Also identified by DOI 10.1002/adma.202413295.
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Abstract
Aluminum scandium nitride (AlScN) has emerged as a promising candidate for next-generation ferroelectric memories, offering a much higher remanent charge density than other materials with a stable ferroelectric phase. However, the inherently high coercive field requires a substantial decrease in film thickness to lower the operating voltage. Significant leakage currents present a severe challenge during the thickness scaling, especially when maintaining compatibility with complementary-metal-oxide-semiconductor (CMOS) fabrication standards. This study adopts a HfN<sub>0.4</sub> bottom electrode, which minimizes lattice mismatch with Al<sub>0.7</sub>Sc<sub>0.3</sub>N (ASN), forming a coherent bottom interface that effectively reduces leakage currents even at thickness < 5 nm. CMOS-compatible HfN<sub>0.4</sub>/ASN/TiN stack, deposited without vacuum break between each layer, demonstrates exceptional scalability, confirming the ferroelectricity of ASN films at thicknesses down to 3 nm. The coercive voltage is decreased to 4.35 V, significantly advancing low-voltage AlScN devices that align with CMOS standards.