Radical oxidation process for fabricating a nonvolatile charge trap memory device

Abstract

A method for fabricating a nonvolatile charge trap memory device is described. The method includes subjecting a substrate to a first oxidation process to form a tunnel oxide layer overlying a polysilicon channel, and forming over the tunnel oxide layer a multi-layer charge storing layer comprising an oxygen-rich, first layer comprising a nitride, and an oxygen-lean, second layer comprising a nitride on the first layer. The substrate is then subjected to a second oxidation process to consume a portion of the second layer and form a high-temperature-oxide (HTO) layer overlying the multi-layer charge storing layer. The stoichiometric composition of the first layer results in it being substantially trap free, and the stoichiometric composition of the second layer results in it being trap dense. The second oxidation process can comprise a plasma oxidation process or a radical oxidation process using In-Situ Steam Generation.

What is claimed is: 
     
         1 . A method comprising:
 subjecting a substrate to a first oxidation process to form a tunnel oxide layer over a channel connecting a source and a drain of the memory device formed in the substrate, wherein the channel comprises polysilicon;   forming a multi-layer charge storing layer over the tunnel oxide layer, wherein the multi-layer charge storing layer comprises an oxygen-rich first layer having a nitride on the tunnel oxide layer in which a stoichiometric composition of the first layer results in it being substantially trap free, and an oxygen-lean second layer comprising a nitride on the first layer in which a stoichiometric composition of the second layer results in it being trap dense; and   subjecting the substrate to a second oxidation process to consume a portion of the second layer and form a high-temperature-oxide layer over the multi-layer charge storing layer.