Nan Ya Technology Corporation

Hsu Yu-Sheng

Ming-Cheng Chang

Yinan Chen

A two-stage method for making buried strap out-diffusions is disclosed. A substrate having a deep trench is provided. A first conductive layer is deposited at the bottom of the deep trench. A collar oxide is formed on sidewalls of the deep trench. A second conductive layer is deposited within the deep trench atop the first conductive layer. The collar oxide is then etched back to a predetermined depth. A third conductive layer is deposited directly on the second conductive layer. A trench top oxide (TTO) layer is formed on the third conductive layer. A spacer is formed on the sidewalls of the deep trench. A portion of the TTO layer is etched away to form a recess underneath the spacer, which exposing the substrate in the deep trench. Thereafter, a doping process is carried out to form a first diffusion region through the recess, followed by spacer stripping. Finally, a thermal process is performed to out-diffuse dopants of the second conductive layer to the substrate through the third conductive layer, thereby forming a second diffusion region that merges with the first diffusion region.

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Tao-Yuan, Taiwan

Hsu Yu-Sheng