Low resistance small metal contact for high temperature application

A reliable small metal contact (∼0.18 μm) withstanding high temperature post-thermal budget (∼800 °C for 30 min) is developed for a bit-line (BL) contact of gigabit scaled dynamic random access memories with capacitor-over BL structure. Cobalt (Co) salicidation on the source/drain regions is indispensable to have low BL contact resistance (Rc). The CoSix layer under the contact hole prevents the contact liner (Ti) from reacting with the sub-silicon. Thus, TiSix agglomeration as well as dopant-TiSix interaction is suppressed even with relatively high postannealing temperature. Thin SiN layer on the CoSix is an effective etch stopper during contact etch and protects the thin CoSix layer from the etch damage. Use of an Ar+ soft inductively coupled plasma cleaning instead of the wet chemical cleaning after contact etch is another key factor to attain a reliable BL contact process. The low Rc and contact leakage are ensured when ion–metal–plasma Ti/TiN liner is utilized.