High yielding self-aligned contact process for a 0.150-μm DRAM technology

This paper describes improvements in the self-aligned contact process for 0.150 μm and 0.175 μm technology generations. Using a dynamic random access memory cell layout, we show that self-aligned contacts can be formed at 0.175 μm ground rules and beyond by using a C₄F₈-CH₂F₂ chemistry. With the improved etch selectivity, gate cap nitride thickness can be reduced, resulting in a smaller aspect ratio for the gate etch, borophosphosilicate glass fill, and contact etch. With a rectangular contact, the area can be increased and the process windows for lithography and etch are improved. The process window for lithography increases by up to 40%, the aspect ratio for the etch and the contact fill is less, and the sensitivity to misalignment is reduced. The combination of rectangular contacts and C₄F₈-CH ₂F₂ chemistry greatly enhances the product yield