| CPC H01L 21/76221 (2013.01) [H01L 21/0217 (2013.01); H01L 21/02271 (2013.01); H01L 21/28211 (2013.01)] | 20 Claims |

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1. A method comprising:
forming an isolation pad oxide layer on a substrate;
forming and patterning a silicon nitride layer on the isolation pad oxide layer;
oxidizing portions of the substrate not covered by the silicon nitride layer to form a LOCOS layer;
subsequent to forming the LOCOS layer, oxidizing the silicon nitride layer in an oxidizing ambient containing a chlorine source to form a silicon dioxide layer; and
thinning the silicon dioxide layer.
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