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

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 (Δ VT) 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 Δ VT 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.