Method for fabricating a nonvolatile sonos memory device
View Patent ↗A nonvolatile memory device and a method for fabricating the same is disclosed, to prevent a “smiling” phenomenon in an ONO layer, thereby improving the programming and erasing characteristics, reliability and yield. The device generally includes a semiconductor substrate; a gate insulating layer, a selection gate and a first insulating layer on the semiconductor substrate; an ONO layer formed on the semiconductor substrate including the selection gate; and a control gate formed on the ONO layer at least partially overlapping with the selection gate.
1. A method for fabricating a nonvolatile memory device comprising:
sequentially stacking a gate insulating layer, a first conductive layer and a first insulating layer on a semiconductor substrate;
patterning the first insulating layer, the first conductive layer and the gate insulating layer to form a selection gate;
forming a second insulating layer at sides of the selection gate by oxidizing an exposed surface of the selection gate;
forming an ONO layer on the semiconductor substrate including the selection gate;
forming a control gate on the ONO layer, partially overlapping with the selection gate and partially overlapping with a channel region of the semiconductor substrate; and
forming source and drain regions by implanting impurity ions in to the semiconductor substrate using the selection gate and control gate as a mask.
2. The method of claim 1 , further comprising forming respective lines connected with the selection gate, the control gate and the source and drain regions.
3. The method of claim 1 , wherein the step of forming the selection gate includes:
selectively etching the first insulating layer and the first conductive layer;
oxidizing the sides of the etched first conductive layer; and
selectively removing the gate insulating layer using the first insulating layer as a mask.
4. The method of claim 1 , further comprising forming conductor lines to the control gate, the selection gate, and the source and drain regions.
5. The method of claim 1 , wherein the first conductive layer comprises polysilicon.
6. The method of claim 1 , wherein the first insulating layer comprises an oxide layer.
7. The method of claim 6 , wherein the first insulating layer further comprises a nitride layer.
8. The method of claim 1 , wherein the first insulating layer comprises a nitride layer.
9. The method of claim 1 , wherein the ONO layer comprises comprising a tunnel oxide layer, a trap nitride layer, and a blocking oxide layer.
10. The method of claim 9 , wherein forming the ONO layer comprises sequentially forming the tunnel oxide layer, the trap nitride layer, and the blocking layer on the semiconductor substrate and the selection gate, including sidewalls of the selection gate.
11. The method of claim 1 , wherein the control gate comprises a polysilicon-containing layer, a metal, a metal alloy, or a conductive metal compound.
12. The method of claim 1 , wherein forming the control gate comprises depositing a second conductive layer, then selectively removing portions of the second conductive layer.
13. The method of claim 12 , wherein the control gate and the ONO layer overlap a portion of the selection gate and a portion of the substrate between the source and drain.
14. The method of claim 1 , further comprising selectively etching the ONO layer using the control gate as a mask.
15. The method of claim 11 , wherein the control gate comprises doped polysilicon.