Semiconductor memory having charge trapping memory cells and fabrication method thereof
View Patent ↗A semiconductor memory having charge trapping memory cells and fabrication method thereof. The direction of current flow of each channel region of the memory transistors runs transversely with respect to the relevant word line, the bit lines are arranged on the top side of the word lines and in a manner electrically insulated from the latter, and electrically conductive local interconnects of source-drain regions are present, which are arranged in sections in interspaces between the word lines and in a manner electrically insulated from the latter and connected to the bit lines, wherein gate electrodes are arranged in trenches at least partly formed in the memory substrate.
1. A method for fabricating a semiconductor memory, comprising:
providing of a substrate having a first polarity in a memory cell array region;
forming of shallow trench isolations in parallel alignment at a distance of one to another in the substrate;
forming of a sacrificial layered structure comprising a sacrificial mask layer above the substrate;
etching of word line trenches in the sacrificial mask layer and substrate in orthogonal alignment as to the shallow trench isolations;
growing of a tunneling dielectric oxide layer in the word line trenches and depositing of a charge trapping storage layer on the tunneling dielectric oxide layer;
depositing of a gate dielectric on top of the storage layer;
depositing of at least one gate conductor material in the word line trenches and back-etch of the gate conductor materials to form recessed portions;
depositing of an electrically insulating material on the gate conductor material;
forming of local interconnect isolations;
etching of local interconnect openings;
forming of source/drain regions;
filling of local interconnect openings with electrically conductive material.
2. The method of claim 1 , comprising wherein the word line layer is polysilicon.
3. The method of claim 1 , comprising wherein etching of the word line trenches is a multi-step process.
4. The method of claim 1 , comprising wherein before growing of a tunneling dielectric oxide layer in the word line trenches a sacrificial oxide layer is grown and removed.
5. The method of claim 1 , comprising wherein a further step of pattering of the storage layer is comprised.
6. The method of claim 5 , wherein pattering of the storage layer comprises:
depositing a conformal masking layer;
coating an organic masking resist onto the masking layer and recessing of the organic masking resist; and
removing of open parts of the masking layer to form sidewall spacers out of the masking layer.
7. The method of claim 5 , wherein pattering of the storage layer comprises:
depositing a conformal masking layer;
etching of the masking layer to form sidewall spacers of the masking layer.
8. The method of claim 1 , comprising depositing a first gate conductor material and a second gate conductor material on the gate dielectric.
9. The method of claim 8 , comprising conformally depositing the first gate conductor material is on the gate dielectric to form a groove for depositing the second gate conductor material.