| 摘要 |
A method for creating isolation structures in a substrate without having to increase the field implant doses to prevent punch through. This particular advantage is achieved by first growing a pad oxide on the substrate. Polysilicon is deposited on top of the pad oxide layer. Next, silicon nitride, used for masking, is deposited on the polysilicon layer. An opening, also called an isolation space, is etched into the three layers, exposing part of the substrate. A first field oxide is grown in the opening. This first field oxide layer is etched to expose a portions of the substrate along the edge of the field oxide region. Then, trenches are etched into the exposed portions of the substrate, and field implantation of dopants is performed. After implantation, a second field oxide layer is grown. The silicon nitride, polysilicon, and pad oxide are then removed, resulting in the isolation structure of the present invention.
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