Method for making DRAM using a single photoresist masking step for making capacitors with node contacts

摘要

A method for forming stacked capacitors for DRAMs using a single photoresist mask and having bottom electrodes self-aligned to node contacts is achieved. A planar silicon oxide (SiO2) first insulating layer is formed over device areas. A first silicon nitride (Si3N4) hard mask layer is deposited and a second insulating layer is deposited. First openings are etched, partially into the first insulating layer, for the capacitor bottom electrodes. A second Si3N4 layer is deposited and etched back to form sidewall spacers in the first openings. The Si3N4 hard mask and spacers are used to etch second openings (node contacts) in the first insulating layer, self-aligned in the first openings and to the source/drain contact areas. A first polysilicon layer is deposited and etched back to form recessed polysilicon plugs in the first openings. A third Si3N4 layer is deposited and etched back to form sidewall spacers on the plugs in the first openings and is used as a mask to etch the polysilicon to form the vertical sidewalls of the bottom electrodes self-aligned to the node contacts. The first insulating layer is recessed to expose the bottom electrodes. An interelectrode dielectric layer is formed on the bottom electrodes, and a patterned second polysilicon layer is used for the top electrodes.