Method to elimate silicide cracking for nand type flash memory devices by implanting a polish rate improver into the second polysilicon layer and polishing it

Abstract

In one embodiment, the present invention relates to a method of forming a flash memory cell, involving the steps of forming a tunnel oxide on a substrate; forming a first polysilicon layer over the tunnel oxide; forming an insulating layer over the first polysilicon layer; forming a second polysilicon layer over the insulating layer by depositing an second polysilicon layer having a first thickness, and then using chemical mechanical polishing to form a second polysilicon layer having a second thickness, wherein the second thickness is at least about 25% less than the first thickness; forming a tungsten silicide layer over the second polysilicon layer by chemical vapor deposition using WF6 and SiH4; etching at least the first polysilicon layer, the second polysilicon layer, the insulating layer, and the tungsten silicide layer thereby defining at least one stacked gate structure; and forming a source region and a drain region in the substrate, thereby forming at least one memory cell.

Dependencies are inferred from the claim text.