DIELECTRICS FOR NANOSYSTEMS 6: MATERIALS SCIENCE, PROCESSING, RELIABILITY, AND MANUFACTURING
225th ECS Meeting date:MAY 11-15, 2014
In this paper we will discuss the key materials issues involved in the successful fabrication of hybrid floating gate (HFG) devices, a solution to scale NAND flash below 20 nm node. In HFG a Si\metal stack replaces the standard poly-Si FG. The metal is required to have a high work function (WF) in order to control the leakage through the inter-gate dielectric (IGD); a high k-value of the IGD is essential to increase the coupling factor of the memory cell. Our reference stack uses TiN(WF 4.7 eV) and Al2O3(k similar to 9) IGD annealed at 1000 degrees C. The metal candidates are Ta1-xAlxNy (WF>4.9eV) and Ru (WF>4.7eV). The high-k IGD of choice are Hf1-xAlxOy, GdxHf1-xOy, GdxSc1-xOy and Sc1-xAl1-xOy. We will show that optimal memory performance is strongly linked to the IGD crystallinity and the thermal stability (inter-diffusion) of the metal-IGD system. The optimal material combination is found to be TiN\HfAlO(k similar to 19) annealed at 800 degrees C.