Method for manufacturing trench isolation

A method for manufacturing a trench isolation in a semiconductor device, said method comprising:

• providing a silicon substrate having a first pad oxide layer and a first silicon nitride layer, wherein said first silicon nitride layer is formed on said first pad oxide layer;
• transferring an isolation region pattern into said first pad oxide layer and said first silicon nitride layer by using a dry etching process to form an anti-diffusion layer mask and expose an active region of said silicon substrate;
• oxidizing said silicon substrate by using a thermal oxidation process to form a first silicon dioxide layer, wherein lateral oxidation on said active region of said silicon substrate underneath said first pad oxide layer, said first silicon nitride layer provides an edge of said first silicon dioxide layer a shape of a bird's beak;
• removing said first silicon nitride layer;
• removing said first pad oxide layer and said first silicon dioxide layer;
• oxidizing said silicon substrate to form a second pad oxide layer on said silicon substrate;
• depositing a second silicon nitride layer on said second pad oxide layer;
• transferring an active region pattern into said second silicon nitride layer, said second pad oxide layer and said silicon substrate to form an isolation trench in an isolation region of said silicon substrate;
• depositing a second silicon dioxide layer on said second silicon nitride layer and said isolation trench to fill said isolation trench;
• planarizing said second silicon dioxide layer to expose said second silicon nitride layer by using a chemical mechanical polishing process;
• removing said second silicon nitride layer;
• and
• removing said second pad oxide layer.

A method for manufacturing a trench isolation in a semiconductor device, said method comprising:

• providing a silicon substrate having a first pad oxide layer and a first silicon nitride layer, wherein said first silicon nitride layer is formed on said first pad oxide layer;
• transferring an isolation region pattern into said first pad oxide layer and said first silicon nitride layer by using a dry etching process to form an anti-diffusion layer mask and expose an active region of said silicon substrate;
• oxidizing said silicon substrate by using a thermal oxidation process to form a first silicon dioxide layer, wherein lateral oxidation on said active region of said silicon substrate underneath said first pad oxide layer, said first silicon nitride layer provides an edge of said first silicon dioxide layer a shape of a bird's beak;
• removing said first silicon nitride layer by using a wet etching process;
• removing said first pad oxide layer and said first silicon dioxide layer by using a wet etching process;
• oxidizing said silicon substrate by using a thermal oxidation process to form a second pad oxide layer on said silicon substrate;
• depositing a second silicon nitride layer by using a low pressure chemical vapor deposition process on said second pad oxide layer;
• transferring an active region pattern into said second silicon nitride layer, said second pad oxide layer and said silicon substrate by using a dry etching process to form an isolation trench in an isolation region of said silicon substrate;
• depositing a second silicon dioxide layer on said second silicon nitride layer and said isolation trench by using a low pressure chemical vapor deposition process to fill said isolation trench;
• planarizing said second silicon dioxide layer to expose said second silicon nitride layer by using a chemical mechanical polishing process;
• removing said second silicon nitride layer;
• and
• removing said second pad oxide layer.