Method and system for erasing a nitride memory device
View Patent ↗The present invention is a method and system for erasing a nitride memory device. In one embodiment of the present invention, an isolated P-well is formed in a semiconductor substrate. A plurality of N-type impurity concentrations are formed in the isolated P-well and a nitride memory cell is fabricated between two of the N-type impurity concentrations. Finally, an electrical contact is coupled to the isolated P-well.
1. A method for erasing a memory device comprising:
creating an isolated P-well in a semiconductor substrate, wherein said creating said isolated P-well comprises:
creating a deep N-well using a first semiconductor fabrication process;
creating a P-well disposed above said deep N-well using a second semiconductor fabrication process; and
creating an N-type sidewell disposed around perimeter of said P-well and perimeter of said deep N-well using a third semiconductor fabrication process;
fabricating a dual-bit nitride memory cell upon said isolated P-well, wherein said dual bit nitride memory cell is disposed between two N-type impurity concentrations formed in said isolated P-well, and wherein said dual-bit nitride memory cell includes a bottom oxide layer, a nitride layer, and a top oxide layer having a higher dielectric constant than said bottom oxide layer;
coupling an electrical contact to said isolated P-well; and
conducting an erase voltage between said dual-bit nitride memory cell and said electrical contact via said isolated P-well.
2. The method for erasing a memory device as recited in claim 1 , further comprising erasing a residual charge in said dual-bit memory cell using said erasing voltage.
3. The method for erasing a memory device as recited in claim 1 , wherein said creating of said deep N-well comprises implanting arsenic in said semiconductor substrate to a depth of approximately 4 to 5 microns.
4. The method for erasing a memory device as recited in claim 1 , wherein said creating of said P-well comprises implanting a dopant in said semiconductor substrate to a depth of approximately 2 to 3 microns.
5. The method for erasing a memory device as recited in claim 1 , wherein said creating of said N-type sidewell comprises implanting arsenic in said semiconductor substrate to a depth of approximately 2 to 3 microns.
6. The method for erasing a memory device as recited in claim 1 , wherein said dual-bit nitride memory cell further includes a control gate, wherein said conducting of said erase voltage comprises conducting a first voltage to said control gate and conducting a second voltage to said electrical contact.
7. The method for erasing a memory device as recited in claim 6 , wherein said conducting of said first voltage comprises conducting a negative voltage to said control gate.
8. The method for erasing a memory device as recited in claim 6 , wherein said conducting of said second voltage comprises conducting a positive voltage to said electrical contact.