Nitride deposition wafer to wafer native oxide uniformity improvement for 0.35 flash erase performance by adding thermal oxide oxidation process

摘要

A new method is provides for the creation of a hardmask over a layer of polysilicon for the etching of floating gate for split-gate flash memory devices. A layer of gate oxide is created over the surface of a substrate, a layer of polysilicon is deposited over the surface of the layer of gate oxide. In a first embodiment of the invention, a layer of native oxide is grown over the surface of the layer of gate material, this layer of gate oxide is used to enhance oxidation of exposed portions of the layer of gate material. In a second embodiment of the invention, enhanced oxidation of exposed portions of the layer of polysilicon is achieved by modifying the conventional sequence of the oxidation process. This latter modification is realized by modifying the forward motion of the substrates through the oxidation furnace or by modifying the sequence in which the substrates move through the oxidation furnace.