Method for forming a tantalum oxide capacitor using two-step rapid thermal nitridation

Abstract

A method for forming a Ta2O5 capacitor on a semiconductor device reduces leakage current and increases cell capacitance by utilizing a two-step rapid thermal nitridation (RTN) process to form a nitride layer on a hemi-spherical grain (HSG) storage node. The first RTN process is performed in a NH3 atmosphere at 800±40° C. for 180±60 seconds, thereby forming a nitride layer having a thickness of about 4 Å. The second RTN process is performed in a NH3 atmosphere at 850±40° C. for 180±60 seconds, thereby increasing the thickness of the nitride layer to at least about 7 Å. Therefore, a nitride layer that is thick enough to act as an oxidation barrier is achieved, but agglomeration of the HSGs on the storage node due to high process temperatures is prevented. To make the structure more readily adaptable to process for manufacturing DRAMs with Ta2O5 dielectric layers, a rapid thermal oxidation (RTO) process can then be performed in an O2 or N2O atmosphere at 850±50° C. for 90±30 seconds to thereby form a combined layer comprising a nitride layer and an oxide layer.

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