Method for manufacturing double-crown capacitors self-aligned to node contacts on dynamic random access memory

摘要

A method is described using a single photoresist mask to make a double- crown-shaped DRAM capacitor self-aligned to the capacitor node contact. After forming the DRAM FETs and the bit lines, a planar BPSG layer, a first polysilicon layer, and a CVD oxide layer are deposited. A node contact photoresist mask is used to form first openings in the CVD oxide in which silicon nitride sidewall spacers are formed. A smaller second opening is etched in the first opening to form node contact openings to the DRAM FET source/drain areas. A conformal second polysilicon layer is deposited to form node contacts in the second openings and over the free- standing sidewall spacers. A planar spin-on glass layer is then used as a self-aligned mask to etch back to expose the second polysilicon layer, which is then removed from the top of the sidewall spacers. After removing the spin-on glass an anisotropic etch is used to form the double- crown-shaped capacitor bottom electrodes self- aligned to the node contacts. The bottom electrode surface is roughened to increase the capacitance area, and the sidewall spacers are removed. An interelectrode dielectric layer and a third polysilicon layer are used to complete the double-crown-shaped stacked capacitors.