Method to etch cu/ta/tan selectively using dilute aqueous hf/hcl solution

Abstract

Copper can be etched with selectivity to Ta / TaN barrier liner and SiC hardmask layers, for example, to reduce the potential copper contamination. The copper film can be recessed more than the liner to further enhance the protection. Wet etch solutions including a mixture of HF and HCl can be used for selective etching copper with respect to the liner material, for example, the copper film can be recessed between 2 and 3 nm, and the barrier liner film can be recessed between 1.5 and 2 nm.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to methods for fabricating an integrated-circuit device, and particularly to selective wet etches processes between copper, tantalum and tantalum nitride.BACKGROUND OF THE INVENTION[0002]Current technologies for fabricating ultra-large scale integrated-circuit devices employ copper interconnects. Interconnections using copper have replaced aluminum in the fabrication of ultra-large scale integrated-circuit devices due to its lower specific resistance and improved electromigration (EM) characteristics.[0003]Usually, the copper interconnects are surrounded by barrier liners, such as tantalum (Ta) and / or tantalum nitride (TaN), to prevent outdiffusion and corrosion of the copper interconnect lines. For example, copper can diffuse into the surrounding dielectric materials at low temperatures, leading to device performance degradation. Copper can also be oxidized and corroded during the standard processing of device fabr...

AI Technical Summary

Benefits of technology

[0009]In some embodiments, methods for selective etching copper with respect to the liner are provided, for example, to reduce the potential copper contamination. The copper film can be recessed more than the liner to further enhance the protection. In some embodiments, the copper film can be recessed between 2 and 3 nm. The liner film can be recessed between 1.5 and 2 nm. In some embodiments, the liner film can include Ta or TaN.

[0013]In some embodiments, the wet etch processes can include a process time between 30 and 60 seconds. The process temperature can be between 25 and 40 C. In some embodiments, a water rinse can be performed, for example, using deionized water at a temperature between 15 and 35 C, such as room temperature, and for a time between 60 and 120 seconds. The rinsing process can remove the etch solution to prevent further etching.

[0014]In some embodiments, a SiC layer can be formed as a hard mask layer on the dielectric layer, which can protect the dielectric layer during the recess of the copper and the liner materials. The copper and the liner materials can be selectively etched with respect to the SiC hard mask, thus providing a recess copper and liner materials, reducing potential copper diffusion damage.

Problems solved by technology

For example, copper can diffuse into the surrounding dielectric materials at low temperatures, leading to device performance degradation.

For example, after the planarization, copper can migrate over time to cause bridges between adjoining copper wirings, leading to the deterioration of leakage current characteristics.

The weak spots thus can decrease operational reliability due to current leakage and thus increase the risk of operational breakdown, such as time dependent dielectric breakdown (TDDB).

In addition, high electric field can be observed at the top edges of the interconnect lines, which can cause operational breakdown or electromigration failures due to the high electrical field concentration.

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