Unique Ferroelectric Fatigue Behavior and Exceptional High Temperature Retention in Al0.93B0.07N Films

TL;DR

This study investigates the fatigue and retention properties of Al0.93B0.07N ferroelectric films, revealing high endurance and exceptional high-temperature retention, with insights into how capacitor architecture influences degradation and performance.

Contribution

It introduces a detailed analysis of fatigue behavior in Al0.93B0.07N films and demonstrates how capacitor design enhances durability and retention at elevated temperatures.

Findings

Al0.93B0.07N films survive up to 10^6 cycles with improved design.

Thermal failures are linked to dielectric breakdown, not surface flashover.

Retention remains high, with over 82% predicted after 10 years at 200°C.

Abstract

This paper reports the fatigue and retention behavior for Al1-xBxN thin films, a member of the novel family of wurtzite ferroelectrics, with an emphasis on the role of capacitor architecture. By modifying the capacitor architecture, and thus thermal and electrical boundary conditions, we create insight regarding the relative importance of intrinsic and extrinsic contributors to the degradation tendencies. Our experiments suggest that bipolar cycling of metal (Pt/W)/Al0.93B0.07N/W/Al2O3 film stacks first induced wake-up, then a region of constant switchable polarization. On additional cycling, the film leakage current increased, and then films underwent dielectric breakdown. For unpatterned first generation Al0.93B0.07N films with 100 nm thick Pt top electrodes survive ~104 bipolar cycles, whereas films with 1000 nm W top electrodes survive ~10^5 cycles before thermal dielectric breakdown. Sentaurus modeling was used to design an SU8 field plate which improved the performance to ~10^6 fatigue cycles. It was found that the thermal failures during fatigue were not due to surface flashover events but were associated with hard breakdown events in the dielectric. The films showed excellent retention of the stored polarization state. As expected, data retention was slightly inferior in the opposite state (OS) measurements. However, it is noted that even after 3.6x10^6 sec (1000 hr). at 200{\deg}C, the OS signal margin still exceeded 200 uC/cm2. The predicted OS retention is 82% after 10 years baking at 200oC.