Epitaxially coated semiconductor wafer, and method for producing an epitaxially coated semiconductor wafer
View Patent ↗Epitaxial wafers with a high concentration of BMD nuclei or developed BMDs just below a denuded zone, and having low surface roughness, are produced by forming an oxynitride layer on a purposefully oxidized epitaxial layer by a short RTA treatment in a nitriding atmosphere, removing the oxynitride layer, and then polishing the epitaxial surface.
1. An epitaxially coated semiconductor wafer, comprising:
a substrate wafer comprising monocrystalline silicon having a front side, rear side, a center, and a periphery;
an epitaxial layer comprising silicon and having a polished surface on the front side of the substrate wafer, wherein the polished surface has an RMS roughness of not more than 0.055 nm in a measurement window having dimensions of 10 μm×10 μm;
a denuded zone extending from the polished surface of the epitaxial layer to the rear side of the substrate wafer as far as a depth which, between the center and the periphery of the semiconductor wafer, is not less than 6 μm and not more than 14 μm, and
a region adjoining the denuded zone and having BMD nuclei which can develop into BMDs by heat treatment, with a peak density of BMD nuclei of not less than 3.5×10 9 cm −3 at a distance of not more than 70 μm from the polished surface of the epitaxial layer.
2. The epitaxially coated semiconductor wafer of claim 1 , which has BMD nuclei which can develop into BMDs whose density at a distance of 50 μm from the polished surface of the epitaxial layer is not less than 70% of the peak density.
3. The epitaxially coated semiconductor wafer of claim 1 , which has BMD nuclei which can develop into BMDs whose density at a distance of 200 μm from the polished surface of the epitaxial layer as far as the rear side of the substrate wafer is not greater than 60% of the peak density.
4. The epitaxially coated semiconductor wafer of claim 2 , which has BMD nuclei which can develop into BMDs whose density at a distance of 200 μm from the polished surface of the epitaxial layer as far as the rear side of the substrate wafer is not greater than 60% of the peak density.
5. A method for producing an epitaxially coated semiconductor wafer, comprising:
providing a substrate wafer comprising monocrystalline silicon, having a front side, a rear side, a center, and a periphery;
depositing an epitaxial layer comprising silicon on the front side of the substrate wafer; treating the epitaxial layer with an oxidant;
treating the epitaxially coated semiconductor wafer with an RTA treatment at a temperature in a temperature range of not less than 1160° C. and not more than 1185° C. for a time period of not less than 15 s and not more than 30 s, wherein the epitaxial layer is exposed to an atmosphere consisting of argon and ammonia and an oxynitride layer forms on the epitaxial layer;
removing the oxynitride layer;
polishing the epitaxial layer; and
recovering an epitaxially coated wafer of claim 1 .