One-time programmable memory and method for making the same

Abstract

A one time programmable nonvolatile memory formed from metal-insulator-semiconductor cells. The cells are at the crosspoints of conductive gate lines and intersecting doped semiconductor lines formed in a semiconductor substrate.

I/We claim: 
     
         1 . An antifuse-based one-time programmable non-volatile memory cell comprising:
 a buried bitline formed in a substrate, the buried bitline of a first conductivity type;   a dielectric layer formed over at least a portion of the buried bitline; and   a conductive gate formed over the dielectric layer, the conductive gate defining a channel region under the conductive gate and dielectric layer;   wherein the channel region does not have electrical interaction other than to said buried bitline or conductive gate.   
     
     
         2 . The memory cell of  claim 1  wherein formed on the sidewalls of the conductive gate are sidewall spacers. 
     
     
         3 . The memory cell of  claim 2  wherein floating regions of a second conductivity type are formed in the substrate spaced away from the channel region by the sidewall spacers. 
     
     
         4 . The memory cell of  claim 2  wherein regions of higher dopant concentration of the first conductivity type are formed in the bitline spaced away from the channel region by the sidewall spacers. 
     
     
         5 . The memory cell of  claim 1  wherein the buried bitline has a graded dopant concentration with a lower dopant concentration near the dielectric layer and a higher dopant concentration deeper in the substrate. 
     
     
         6 . The memory cell of  claim 1  wherein said dielectric layer is thicker proximal to at least a portion of the edge of the channel region than to the center of the channel region. 
     
     
         7 . The memory cell of  claim 1  wherein the buried bitline is formed from standard n-well implants. 
     
     
         8 . A memory array comprised of a plurality of antifuse-based one-time programmable non-volatile memory cells, the memory array comprising:
 a plurality of buried bitlines formed in a substrate, the buried bitline of a first conductivity type;   a dielectric layer formed over at least a portion of the buried bitlines; and   a plurality of conductive gate wordlines formed over the dielectric layer, the conductive gate wordlines intersecting with the plurality of buried bitlines, the memory cells located at the intersection of said conductive gate wordlines and buried bitlines, further wherein a channel region is defined under the intersection of said conductive gate wordlines and buried bitlines and dielectric layer;   wherein the channel region does not have electrical interaction other than to said buried bitline or conductive gate.   
     
     
         9 . The memory array of  claim 8  wherein formed on the sidewalls of the conductive gate of the memory cells are sidewall spacers. 
     
     
         10 . The memory array of  claim 9  wherein floating regions of a second conductivity type are formed in the substrate spaced away from the channel region by the sidewall spacers. 
     
     
         11 . The memory cell of  claim 7  wherein regions of higher dopant concentration of the first conductivity type are formed in the bitline spaced away from the channel region by the sidewall spacers. 
     
     
         12 . The memory array of  claim 8  wherein the buried bitlines have a graded dopant concentration with a lower dopant concentration near the dielectric layer and a higher dopant concentration deeper in the substrate. 
     
     
         13 . The memory array of  claim 8  wherein said dielectric layer is thicker proximal to at least a portion of the edge of the channel region than to the center of the channel region. 
     
     
         14 . The memory array of  claim 9  wherein the sidewall spacers of adjacent conductive gate wordlines completely span the space between the adjacent gate wordlines. 
     
     
         15 . The memory array of  claim 8  wherein shallow trench isolations are formed between the burled bitlines. 
     
     
         16 . The memory array of  claim 8  wherein buried bitlines are formed from standard n-well implants.