Method of fabricating non-volatile memory cell adapted for integration of devices and for multiple read/write operations
A method of manufacturing a non-volatile memory cell includes forming a bottom dielectric layer and a charge trapping layer on a substrate sequentially. The electron trapping layer is patterned to form a trench exposing a portion of the bottom dielectric layer. A top dielectric layer is formed over the substrate and covers the electron trapping layer and the exposed bottom dielectric layer. A conductive layer is then formed on the top dielectric layer. The conductive layer, the top dielectric layer, the electron trapping layer and the bottom dielectric layer are patterned to form a stacked structure, wherein a width of the stacked structure is larger than a width of the trench. A source/drain region is formed in the substrate adjacent to the edges of the stacked structure. Because the electron trapping layer of the memory cell is divided into two isolation structures according to the invention, it is adapted for the integration of devices and for long-time operation.
1. A method of fabricating a non-volatile memory cell, comprising:
forming a bottom dielectric layer, a charge trapping layer, a first top dielectric layer and a mask layer on a substrate sequentially;
etching the mask layer for forming a first wench exposing a portion of the first top dielectric layer;
forming a plurality of first spacers on sidewalls of the first trench;
using the first spacers as an etching mask and etching the first top dielectric layer and the charge trapping layer for forming a second trench;
removing the first spacers;
forming a second top dielectric layer over the substrate, covering surfaces of the second trench and the first trench;
forming a conductive layer in the first trench and the second trench;
removing the conductive layer and the second top dielectric layer outside of the first trench and the second trench for exposing the mask layer;
removing the exposed mask layer;
using the conductive layer as a mask, removing the first top dielectric layer, the charge trapping layer and the bottom dielectric layer for forming a stacked structure; and
forming source/drain regions in the substrate adjacent to edges of the stacked structure.
2. The method of fabricating a non-volatile memory cell of claim 1 , before forming the source/drain regions, further comprising:
forming a plurality of lightly doped regions in the exposed substrate; and
forming a plurality of second spacers on the sidewalls of the stacked structure.
3. The method of fabricating a non-volatile memory cell of claim 1 , wherein the step of forming the bottom dielectric layer comprises forming a silicon oxide layer on a surface of the substrate by a thermal oxidation process.
4. The method of fabricating a non-volatile memory cell of claim 1 , wherein the step of forming the charge trapping layer comprises forming a silicon nitride layer on the bottom dielectric layer by a chemical vapor deposition process.
5. The method of fabricating a non-volatile memory cell of claim 1 , wherein the material of the mask layer comprises silicon nitride.
6. The method of fabricating a non-volatile memory cell of claim 1 , wherein the material of the first spacers comprise polysilicon.
7. The method of fabricating a non-volatile memory cell of claim 1 , wherein the material of conductive layer comprises polysilicon.
8. The method of fabricating a non-volatile memory cell of claim 1 , wherein the material of the charge trapping layer is selected from a group consisting of silicon nitride, tantalum oxide, SrTiO 3 and hafnium oxide.
9. The method of fabricating a non-volatile memory cell of claim 1 , wherein the material of the first top dielectric layer and the second top dielectric layer comprises silicon oxide.
10. The method of fabricating a non-volatile memory cell of claim 1 , wherein the step of removing the conductive layer and the second top dielectric layer outside of the first wench and the second trench is a chemical mechanical polishing process or an etch-back process.
11. The method of fabricating a non-volatile memory cell of claim 1 , wherein the step of removing the mask layer comprises dry etching.