Fowler–Nordheim Stress-Induced Degradation of Buried-Channel-Array Transistors in DRAM Cell for Cryogenic Memory Applications

Abstract

The degradation of the fin-type buried-channel-array transistor (BCAT) in dynamic random access memory (DRAM) cell is investigated under Fowler–Nordheim stress at various temperatures, including 77 K. While the increase in the OFF current is dominated by the Shockley–Read–Hall junction leakage, the threshold voltage shift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta } {V}_{T}$ </tex-math></inline-formula> ) comprises a positive component due to the interface trap generation and a negative component resulting from the electric field concentration-induced charge trapping into the gate insulator bulk, with respective activation energies of 0.22 and 0.13 eV. Furthermore, based on the consistency between the experimentally decomposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta } {V}_{T}$ </tex-math></inline-formula> components and the simulated ones, it is found that the anode hole injection dominates the degradations of the wordline-active operation and refresh time in cryogenic DRAM.