Fabrication and Characterization of NOR-Type Tri-Gate Flash Memory with Improved Inter-Poly Dielectric Layer by Rapid Thermal Oxidation

Floating-gate (FG)-type tri-gate flash memories with an improved inter-poly dielectric (IPD) layer have been successfully fabricated by introducing a newly developed rapid thermal oxidation (RTO) process, and their NOR-mode operation including threshold voltage ($V_{\text{t}}$) variations before and after one program/erase (P/E) cycle have been systematically investigated. It was experimentally confirmed that the gate breakdown voltage (BV\text{g) is greatly increased from 12 to 19 V by introducing the RTO process thanks to the high quality and thin thermal silicon dioxide (SiO2) formation on the FG surface and etched edge regions, which effectively blocks the leakage pass of the IPD layer. A source--drain (SD) breakdown voltage (BV\text{DS) as high as 4.5 V was obtained even when the gate length ($L_{\text{g}}$) was as small as 117 nm. It was also experimentally confirmed that the memory window increases with increasing gate voltage ($V_{\text{g}}$) in NOR-mode programming thanks to the increased efficiency of channel hot electron (CHE) injection. The developed tri-gate flash memory with improved IPD layer is useful for the further scaling of NOR-type flash memory.