Patent ID: 8222114

Claim:
A manufacturing process for a collector and a buried layer of a bipolar transistor, comprises: step 1, depositing an ONO (oxide nitride oxide) hard mask on a silicon substrate surface; etching shallow trenches on the silicon substrate, wherein the depth of the shallow trenches is less than 2 μm; wherein the ONO hard mask includes a silicon oxide (SiO 2 ) layer in the bottom, silicon nitride (Si 3 N 4 ) in the middle and silicon oxide on the top; step 2, depositing a silicon oxide film on the ONO hard mask; etching back the oxide film thus forming a silicon oxide spacer is on sidewalls of the shallow trenches; step 3, doping the bottoms of shallow trenches with an impurity by ion implantation to form doped regions in the substrate near the bottom of the shallow trenches; step 4, stripping the silicon oxide film by wet etch; step 5, filling dielectric into the shallow trenches thus forming shallow trench isolations (STIs); step 6, annealing the silicon substrate with a temperature anneal process to link the doped regions between the STIs through lateral diffusion thus forming a pseudo buried layer; step 7, implanting the active region between the STIs and above the pseudo buried layer with one or more ion implantations; thus converting it into the collector.