Optimization of Ru Based Hybrid Floating Gate for Planar NAND Flash

The required transition from Control Gate wrap-around to planar structure for NAND flash scaling below 20nm node causes important loss of coupling factor. In order to recover the Programming window, we develop a Hybrid Floating Gate using Ru as high work-function metal. With a proper nitridation of the underlying Si and ALD technique, we obtain a continuous Ru layer as thin as 2nm that is thermally stable in contact with Si. Thanks to the higher work function of Ru, a programming window of more than 10V has been be achieved.