SONOS ONO stack scaling
A method of scaling a nonvolatile trapped-charge memory device and the device made thereby is provided. In an embodiment, the method includes forming a channel region including polysilicon electrically connecting a source region and a drain region in a substrate. A tunneling layer is formed on the substrate over the channel region by oxidizing the substrate to form an oxide film and nitridizing the oxide film. A multi-layer charge trapping layer including an oxygen-rich first layer and an oxygen-lean second layer is formed on the tunneling layer, and a blocking layer deposited on the multi-layer charge trapping layer. In one embodiment, the method further includes a dilute wet oxidation to densify a deposited blocking oxide and to oxidize a portion of the oxygen-lean second layer.
1. A method of fabricating a nonvolatile trapped-charge memory device, comprising:
forming a channel region in a substrate, the channel region electrically connecting a source region and a drain region in the substrate, wherein the channel region comprises polysilicon;
forming a tunneling layer on the substrate over the channel region, wherein forming the tunneling layer comprises oxidizing the substrate to form an oxide film and nitridizing the oxide film;
forming a multi-layer charge trapping layer comprising an oxygen-rich first layer on the tunneling layer and an oxygen-lean second layer over the first layer; and
forming a blocking layer on the multi-layer charge trapping layer,
wherein forming the multi-layer charge trapping layer further comprises forming an anti-tunneling layer comprising an oxide separating the first layer from the second layer.
2. The method of claim 1 , wherein forming the channel region comprises recrystallizing the polysilicon.
3. The method of claim 1 , further comprising densifying the blocking layer with an oxidizing anneal, wherein the oxidizing anneal oxidizes a portion of the oxygen-lean second layer of the multi-layer charge trapping layer proximate to the blocking layer.
4. The method of claim 1 , wherein forming the tunneling layer further comprises reoxidizing the nitridized oxide film by exposing the substrate to O 2 .
5. The method of claim 4 , wherein forming the tunneling layer further comprises renitridizing the reoxidized nitridized oxide film by exposing the substrate to NO.
6. The method of claim 1 , wherein at least one of the first layer and second layer of the multi-layer charge trapping layer comprise oxynitride.
7. A method of fabricating a nonvolatile trapped-charge memory device, comprising:
forming a channel region in a substrate;
forming a tunneling layer over the channel region, wherein forming the tunneling layer comprises oxidizing a surface of the substrate to form an oxide film and nitridizing the oxide film; and
forming a multi-layer charge trapping layer on the tunneling layer, the multi-layer charge trapping layer comprising an oxygen-rich first layer, an oxygen-lean second layer, and an anti-tunneling layer comprising an oxide separating the first layer from the second layer.
8. The method of claim 7 , further comprising forming a blocking layer on the multi-layer charge trapping layer.
9. The method of claim 8 , further comprising densifying the blocking layer with an oxidizing anneal, wherein the oxidizing anneal oxidizes at least a portion of the oxygen-lean second layer of the multi-layer charge trapping layer proximate to the blocking layer.
10. The method of claim 7 , wherein the channel region comprises polysilicon.
11. The method of claim 10 , wherein forming the channel region comprises recrystallizing the polysilicon.
12. The method of claim 7 , wherein forming the tunneling layer further comprises reoxidizing the nitridized oxide film by exposing the substrate to O 2 .
13. The method of claim 12 , wherein forming the tunneling layer further comprises renitridizing the reoxidized nitridized oxide film by exposing the substrate to NO.
14. The method of claim 7 , wherein at least one of the first layer and second layer of the multi-layer charge trapping layer comprise oxynitride.