Influence of tantalum/tantalum nitride barriers and caps on the high-temperature properties of copper metallization for wide-band gap applications

• Electronic devices and circuits based on wide-band gap (WBG) semiconductors and intended for operation at temperatures significantly exceeding 300 degrees C are currently being developed. It is important that the adjunct metallization matches the high-temperature properties of the devices. In the case of the technologically important Cu metallization, the most frequently used cap and barrier layer materials are Ta, TaN and combinations of these. They stabilize the interconnects and prevent Cu from diffusing into the surrounding material. In this study, different combinations of Ta and TaN layers are evaluated electrically and morphologically after high-temperature treatments. The cap/Cu/barrier stack shows an appreciable increase in sheet resistance above 600 degrees C for the asymmetric combinations Ta/Cu/TaN and TaN/Cu/Ta. This degradation is shown to be closely related to a substantial diffusion of Ta across the Cu film and on to the TaN layer, where Ta1+xN forms. The symmetrical combinations Ta/Cu/Ta and TaN/Cu/TaN show only small changes in sheet resistance on even after anneals at 800 degrees C. A less pronounced Ta diffusion into the Cu film is found for the Ta/Cu/Ta combination. The experimental observations are interpreted in terms of Cu grain growth, Ta segregation in the Cu grain boundaries and morphological degradation of the Cu film.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Nyckelord

Wide band gap application

Copper metallization

High-temperature

Tantalum

Tantalum nitride

Publikations- och innehållstyp

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