Macronix International Co., Ltd.

Shu-Ya Hsu

June-Min Yao

Cheng-Shun Chen

Multiple oxide layers with different thicknesses are formed on a semiconductor substrate with a silicon surface, having a first and second region. A sacrificial oxide layer is formed on the silicon surface to cover both the first region and the second region, with a mask layer formed on the surface of the sacrificial oxide layer. By defining and patterning the mask layer, a first opening and a second opening, having predetermined surface areas, are formed in portions of the first and second regions of the mask layer to expose portions of the. The sacrificial oxide layer has a surface area equal to the first predetermined surface area, and portions of the sacrificial oxide layer having a surface area equal to the second predetermined surface area. A linear nitrogen doping process is then performed to simultaneously implant nitrogen ions with a first and second predetermined concentration into the first and second region, through the first opening and the second opening, respectively. Thereafter, the mask layer and the sacrificial oxide layer are removed, respectively. An oxidation process is performed to two silicon oxide layers with different thicknesses in the first and second regions.

Method of forming multiple oxide layers with different thicknesses in a linear nitrogen doping process

The invention utilizes introductions of oxygen and hydroxyl to perform an in situ steam generated (ISSG) process to anneal and reoxidize a conventional sidewall oxide layer in a shallow trench isolation. The ISSG annealing process renders the conventional sidewall oxide layer much less stress. The electrical property of the active regions and the isolation quality between the active regions can be assured.

Method for reducing stress of sidewall oxide layer of shallow trench isolation

The invention utilizes introductions of oxygen and hydroxyl to perform an in situ steam generated process to reoxidize a conventional sidewall oxide layer and density the oxide in a shallow trench isolation. The ISSG process renders the conventional sidewall oxide layer much less stress and encroachment. The electrical property of the active regions and the isolation quality between the active regions can be assured. The ISSG process can densify the oxide in a shallow trench isolation to prevent the oxide from being lost in the following clean process.

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Yun-Lin, Taiwan

Shu-Ya Hsu