Trench isolation method for semiconductor devices
AssigneeMotorola, Inc.
InventorsAndrew G. Nagy, Robert J. Mattox
Life of this patent
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Abstract
A method is described for forming dielectric filled isolation trenches in semiconductor substrates in which a differentially etchable etch-stop layer is provided above the surface of the substrate during the trench filling process so that the height of the trench filling relative to the surface of the substrate may be adjusted for optimum overall results during subsequent fabrication steps and so that the substrate surface may be protected from contact with the etching reagents used during planarization of the trench filling material. This avoids damage to the substrate surface and permits improved surface planarity.
Claims18
A method for forming an isolation wall in a semiconductor device, comprising:
- providing a semiconductor substrate having a principal surface;
- forming a dielectric layer on the principal surface;
- forming a polycrystalline semiconductor layer on the dielectric layer;
- forming a masking layer having an opening on the polycrystalline layer;
- removing a portion of the polycrystalline layer and the dielectric layer and the substrate underneath the opening to form a trench extending through the polycrystalline layer and the dielectric layer and into the substrate;
- depositing a first material comprising a silicon oxy-nitride overlying the polycrystalline layer and in the trench to substantially fill the trench at least to the polycrystalline layer;
- removing the first material above the polycrystalline layer thereby exposing a first upper surface of the first material in the trench;
- etching a crevice in the first upper surface of the first material in the trench;
- filling the crevice with a second material comprising silicon nitride extending above the polycrystalline layer;
- etching the second material to expose the polycrystalline layer, the first upper surface, and a second upper surface of the second material so that the second upper surface is substantially level with the first upper surface;
- and
- removing the polycrystalline layer.
A method for providing a dielectric filled trench extending into a semiconductor substrate, comprising:
- providing a semiconductor substrate having a principal surface;
- forming a first layer on the substrate surface, wherein the first layer is a dielectric differentially etchable with respect to the substrate;
- forming a second layer on the first layer, wherein the second layer comprises polysilicon and is differentially etchable with respect to the first layer;
- providing a masking material over the second layer and forming a first opening therein extending to the second layer;
- through the first opening, etching underlying portions of the second layer and first layer to expose an underlying portion of the substrate;
- etching the underlying portion of the substrate to form a trench therein extending into the substrate;
- depositing a third layer in the trench and extending over the second layer, wherein the third layer is differentially etchable with respect to the second layer;
- removing the third layer extending over the second layer, leaving part of the third layer in the trench;
- forming a second opening extending at least partly into the third layer in the trench;
- filling the second opening with a fourth layer extending over the second layer, wherein the fourth layer is differentially etchable with respect to the second layer;
- removing the fourth layer above the second layer while leaving the fourth layer in the second opening;
- and
- removing the second layer.
Dependencies are inferred from the claim text.