Method of fabricating an isolation structure in an integrated circuit

A method for fabricating an isolation structure in an integrated circuit, comprising the steps of:

• preparing a semiconductor substrate;
• forming an adhesive layer over the substrate;
• forming a hard mask, layer over the adhesive layer;
• performing a selective etching process to each away selected portions of the etch-end layer, the hard mask layer, and the adhesive layer but not exposing the substrate to thereby form an opening in the etch-end layer and the hard mask layer above the adhesive layer;
• forming a sidewall spacer on the sidewall of the opening with the adhesive layer at the bottom of the second sidewall spacer being still entirely covered by the sidewall spacer;
• performing an etching process through the opening to etch successively through the sidewall spacer and the part of the adhesive layer underlying the sidewall spacer to a predefined depth into the substrate to thereby form a trench in the substrate;
• and
• performing a thermal oxidation process to oxidize the exposed part of the substrate in the trench into a silicon dioxide plug which fills the trench entirely, wherein the silicon dioxide plug in the trench constitutes an STI structure serving as the intended isolation structure.

A method for fabricating an isolation structure in an integrated circuit, comprising steps of:

• preparing a semiconductor substrate;
• forming an adhesive layer over the substrate;
• forming a hard mask layer over the adhesive layer;
• forming an etch-end layer over the hard mask layer;
• performing a selective etching process to each away selected portions of the etch-end layer, the hard mask layer, and the adhesive layer but not exposing the substrate to thereby form an opening in the etch-end layer and the hard mask layer above the adhesive layer;
• forming a sidewall spacer on the sidewall of the opening, with the adhesive layer at the bottom of the opening that is not covered by the sidewall spacer being entirely removed to expose the underlying, part of the substrate;
• performing a thermal oxidation process to oxidize the exposed part of the substrate at the bottom of the opening into a FOX layer serving as the intended isolation structure.