Method for forming trench isolation structures
AssigneeNCR Corporation
InventorsSteven H. Rogers, Randall S. Mundt, Denise A. Kaya
Life of this patent
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Abstract
A method for forming trench isolation oxide using doped silicon dioxide which is reflowed at elevated temperatures to collapse any voids therein and produce surface planarity. An underlying layered composite selected from oxide, polysilicon and silicon nitride permits the formation and reflow of the doped isolation oxide and remains in place in the trench to contribute to the trench isolation structure.
Claims16
A process for forming a composite trench isolation structure in a substrate, comprising:
- forming a trench in the substrate;
- forming a polysilicon etch-stop layer on the trench walls;
- forming an oxidation-and dopant-blocking silicon nitride layer on the etch-stop layer;
- filling the trench will silicon dioxide doped to approximately three to nine weight percent of n-type or p-type impurities;
- heating the resulting structure for a time sufficient to reflow the oxide to thereby collapse voids therein and provide a relatively smooth upper surface;
- etching back the oxide to remove the oxide outside the trench areas;
- heating the resulting structure to outgas the impurity dopant from the surface-adjacent region of the oxide;
- simultaneously or separately to the oxide etch-back step, removing the nitride blocking layer outside the trench;
- and removing the etch-stop layer from at least selected regions outside the trench;
- whereby the nitride blocking layer prevents oxidation and doping the underlying structure during the reflow and outgassing steps and the polysilicon layer prevents etching of the underlying structure during the oxide and nitride removal.
A process for forming a composite trench isolation structure in a substrate, comprising:
- forming a trench in the substrate;
- forming an oxidation-and dopant-blocking silicon nitride layer on the trench walls;
- forming a polysilicon etch-stop layer on the blocking layer;
- filling the trench with silicon dioxide doped to approximately three to nine weight percent of n-type or p-type impurities;
- heating the resulting structure for a time sufficient to reflow the oxide to thereby collapse voids therein and provide a relatively smooth upper surface;
- etching back the oxide to remove the oxide outside the trench areas;
- heating the resulting structure to outgas the impurity dopant from the surface-adjacent region of the oxide;
- removing the etch-stop layer as required from selected regions outside the trench;
- and removing the nitride blocking layer from selected regions outside the trench;
- whereby the nitride blocking layer prevents oxidation and doping of the underlying structure during the reflow and outgassing steps and the polysilicon layer prevents etching the underlying structure during the oxide removal.
A process for forming a trench oxide isolation structure in a substrate, comprising:
- forming an etch mask on the substrate to define the trench surface configuration;
- etching the substrate in the presence of the mask;
- forming a stress relief layer on the trench walls;
- forming an etch-stop layer on the stress relief layer;
- forming an oxidation and dopant blocking layer on the etch-stop layer;
- filling the trench with silicon dioxide isolation dielectric doped to approximately 3-9 weight percent with n-type or p-type impurities;
- heating the resulting structure for a time sufficient to reflow the isolation oxide layer to thereby collapse voids therein and provide a relatively smooth upper surface;
- etching back the oxide to a desired thickness to expose the blocking layer;
- heating the resulting structure to outgas the impurity dopant from the surface adjacent region of the oxide;
- removing the blocking layer from at least selected regions outside the trench structure;
- and removing the etch-stop layer from selected regions outside the trench structure.
Dependencies are inferred from the claim text.