UV-blocking etch stop layer for reducing UV-induced charging of charge storage layer in memory devices in BEOL processing
View Patent ↗A method of protecting a charge trapping dielectric flash memory cell from UV-induced charging, including fabricating a charge trapping dielectric flash memory cell in a semiconductor device; depositing over the charge trapping dielectric flash memory cell at least one UV-protective layer; forming at least one layer over the at least one UV-protective layer; and etching the at least one layer to form an opening therein with an etchant species selective to stop on a layer below the at least one UV-protective layer, wherein the UV-protective layer comprises a substantially UV-opaque material.
1. A method of protecting a charge trapping dielectric flash memory cell from UV-induced charging, comprising:
fabricating a charge trapping dielectric flash memory cell and surrounding the memory cell with a first interlevel dielectric layer (ILD) that includes a conductive plug to establish electrical connection to a conductive region of a substrate upon which a stack gate of the memory cell is formed;
depositing a UV-protective layer over the charge trapping dielectric flash memory cell and the first ILD layer, the UV-protective layer including a UV-opaque etch stop layer;
etching the UV-protective layer to form an opening therein with an etchant species selective to stop on a layer below the at least one UV-protective layer; and
filling the opening in the UV-protective layer to form an electrode vertically traversing the entire UV-protective layer and physically contacting an upper surface of the conductive plug.
2. The method of claim 1 , wherein the UV-protective layer protects the charge trapping dielectric flash memory cell from damage resulting from UV exposure during BEOL processing of the charge trapping dielectric flash memory device.
3. The method of claim 1 , wherein the UV-opaque material comprises one or more of silicon-rich silicon dioxide, silicon-rich silicon nitride, silicon-rich silicon carbide, silicon-rich SiCN, carbon polymers, high-K dielectric materials and graded films.
4. The method of claim 1 , further comprising depositing a second ILD layer over the UV-protective layer and electrode, the second ILD layer including at least a sub-layer of a UV-opaque material.
5. The method of claim 1 , wherein the UV-opaque material comprises a refractive index greater than about 1.5.
6. The method of claim 5 , wherein the refractive index is in the range from about 1.55 to about 1.8.
7. The method of claim 1 , wherein the UV-protective layer is deposited by CVD, LPCVD or APCVD.
8. The method of claim 4 , further comprising depositing at least a third ILD layer over the second ILD layer, the third ILD layer including at least a sub-layer of a substantially UV-opaque material.
9. The method of claim 1 , wherein an upper surface of the electrode is in substantially the same plane as an upper surface of the portions of the UV-protective layer remaining after etching.
10. The method of claim 4 , further comprising forming a second conductive plug in the second ILD, the second conductive plug contacting an upper surface of the electrode.