A novel trench capacitor enhancement approach by selective liquid-phase deposition

For the first time, a novel and simple trench bottle integrated process is demonstrated on dynamic random access memory (DRAM) manufacturing by selective liquid phase deposition (S-LPD) oxide. After photoresist (PR) filled into a deep trench (DT) and was recess etched at around 1.3 μm depth, LPD oxide can be selected as a deposit onto the DT sidewall but not as a deposit on the PR surface. This S-LPD oxide is formed by using hexa-fluosilic acid (H₂SiF₆) and water without H₃BO₃. After the PR is removed, the LPD oxide becomes a protective layer on DT upper portion. Thus, the DT bottom area can be enlarged to form a trench bottle by NH₄OH wet etching. Compared to conventional DT trench, 20% of capacitance was enhanced by this S-LPD process. This novel and low-cost method is for the first time demonstrated on 200-mm wafer 110-nm trench DRAM technology.