Patent ID: 6969648
Filing Date: 2005-11-29
Classification: H01L

Abstract:
1. A method for forming a buried plate in a trench capacitor, the method comprising the steps of: forming at least one trench with a sidewall in a semiconductor substrate; non-conformally partially filling the trench with a dopant source material to form a dopant source having a top surface below a top of the trench, the dopant source material containing at least one dopant; covering the sidewall of the trench above the dopant source with a second material; heating the substrate to cause the dopant to diffuse into the substrate in the trench not covered by the second material, thereby forming the buried plate; wet etching the trench such that the cross section of the upper portion of the trench is squared while the lower portion of the trench is protected by the dopant source material; and removing the dopant source material from the trench.