Patent ID: 7704849

Claim:
A method of forming trench isolation in silicon of a semiconductor substrate, comprising: forming a first mask over silicon of a semiconductor substrate, the first mask comprising first trenches formed there-through running in a first major direction over the substrate, the first mask comprising a hardmask layer; plasma etching first trenches into the silicon of the semiconductor substrate using the first mask, the plasma etching of the first trenches into the silicon comprising forming an etching plasma using precursor gases comprising SF 6 , an oxygen-containing compound, and a nitrogen-containing compound; forming a second mask over the first trenches, the second mask comprising second trenches formed there-through running in a second major direction over the substrate which is orthogonal to the first major direction, the second mask comprising the hardmask layer of the first mask and not crossing the first trenches; plasma etching second trenches into the silicon of the semiconductor substrate using the second mask, the plasma etching of the second trenches into the silicon comprising forming an etching plasma using precursor gases comprising SF 6 , an oxygen-containing compound, and a nitrogen-containing compound; and after plasma etching the second trenches, depositing insulative trench isolation material to within the first and second trenches in the silicon.