Method of fabricating an enhanced dynamic random access memory (DRAM) cell capacitor using multiple polysilicon texturization

Abstract

Abstract A DRAM cell having a doped monocrystalline silicon substrate for the cell's lower capacitor plate whose surface has been texturized multiple times to enhance cell capacitance. After texturization, a thin silicon nitride layer is deposited on top of the texturized substrate, followed by the deposition of a poly layer, which functions as the cell's upper, or field, capacitor plate. The nitride layer, conformal and thin compared to the surface texture of the mono substrate, transfers the texture of the substrate to the cell plate layer. The effective capacitor plate area is substantially augmented, resulting in a cell capacitance increase of at least approximately fifty percent compared to a conventional planar cell utilizing identical wafer area. The substrate is texturized by texturizing a thin polycrystalline silicon (poly) starter layer that has been deposited on top of the substrate by using an anisotropic etch or wet oxidation step, and then allowing the poly starter layer to be consumed, transferring the texture created on the poly starter layer to the underlying substrate. By subjecting the starter layer to either an etch or an oxidation step, atoms at the grain boundaries of the starter layer react more rapidly, thus establishing the texturization pattern. Once established, the starter layer's texturization pattern is transferred to the monocrystalline silicon surface by either etching or oxidizing the starter layer. Performing this texturization process multiple times produces greater texturization due to the consumption of the successive poly starter layers along their respective, uniquely superimposed grain boundaries.

Inventors

• 👤 Aftab Ahmad
• 👤 Pierre C. Fazan
• 👤 Ruojia Lee

Bibliographic Details