IMEC, NSC Develop Copper-Top (Cu-top) Interconnect Technology

IMEC successfully transferred its Copper-Top (Cu-top) interconnect process technology to National Semiconductor’s production facility in Malacca Malaysia. The Cu-top technology is a low resistance, post-passivation interconnect module particularly suited for analog and mixed-signal applications. It improves system-efficiency and results in a significant chip-size reduction of such semiconductor devices.

The Cu-top module can be added to any semiconductor product wafer for current carrying capability. The sheet resistance of the interconnect layer is much lower than today’s standard back-end aluminum (Al) interconnects, therefore, making the technology especially suited for analog and mixed-signal applications where relatively large electrical currents are used.

The technology overcomes the resistive voltage drop and power-loss caused by the low conductivity of traditional interconnects resulting in a significant increase of the system efficiency. Cu top prevents the use of wide metal lines and hence reduces chip areas.

The key feature of this technology is the use of Cu plating in a photoresist pattern, allowing for a small line width to enable a high-density high-current interconnect layer. The contacts through the 2µm thick IC passivation have a diameter of only 3µm and have a very good contact resistance between the plated Cu and the underlying Al layer. The Cu layer on the chip is protected by a 10µm thick polymer dielectric layer.

This layer is photo-defined to clear scribe lanes and bonding pads. The Cu bonding pads are covered with an Al metallization to allow for testing and wire-bond packaging.

The process development and technology transfer results from a three-year close collaboration between IMEC’s thin-film technology group and a team from National Semiconductor Santa Clara, California (USA) and Malacca. After procurement and installation of new equipment in the National Semiconductor’s Malacca facility, the technology was smoothly transferred to NSC.

IMEC’s collaboration with National Semiconductor is currently being continued to develop a significantly thicker version of the technology, resulting in a further reduction of the sheet resistance and consequently a higher power performance of analog circuits.

About IMEC
IMEC is a world-leading independent research center in nanoelectronics and nanotechnology. Its research focuses on the next generations of chips and systems, and on the enabling technologies for ambient intelligence. IMEC’s research bridges the gap between fundamental research at universities and technology development in industry. Its unique balance of processing and system know-how, intellectual property portfolio, state-of-the-art infrastructure and its strong network of companies, universities and research institutes worldwide position IMEC as a key partner for shaping technologies for future systems.

As an expansion of its wireless autonomous microsystems research, IMEC has created a legal entity in the Netherlands. Stichting IMEC Nederland runs activities at the Holst Centre, an independent R&D institute that develops generic technologies and technology platforms for autonomous wireless transducer solutions and systems-in-foil.

IMEC is headquartered in Leuven, Belgium, and has representatives in the US, China and Japan. Its staff of more than 1450 people includes more than 500 industrial residents and guest researchers. In 2005, its revenue was EUR 197 million.

About National Semiconductor
National Semiconductor, the industry’s premier analog company, creates high-value analog devices and subsystems. National’s leading-edge products include power management circuits, display drivers, audio and operational amplifiers, interface products and data conversion solutions. National’s key analog markets include wireless handsets, displays and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications. Headquartered in Santa Clara, Calif., National reported sales of $2.16 billion for fiscal 2006, which ended May 28, 2006.