Copper interconnects replace Aluminum interconnects

LONDON: The evolution to copper interconnects for memory devices suddenly shot up in the year 2009. According to Robert Castellano, president of The Information Network, even as overall semiconductor equipment sales decreased above 40 percent in the year 2009, equipment directly tied to the copper interconnect part of semiconductor manufacturing decreased just by 8.7 percent,

Idaho-based Micron Technology Inc was the initial DRAM manufacturer to produce commodity DRAM with copper, as an alternative for aluminum, in late 2006. Elpida followed the similar footsteps a year later, according to analyst. Subsequently all the memory providers, led by Samsung Electronics Co. Ltd., used up large sums of money in the upgrade of their wafer fabs to copper and this affected purchases of copper deposition equipment and materials in the year 2009.

The impact of this entire evolution on processing equipment was most apparent in equipment used with customary aluminum interconnects. The combination of copper into memory devices presents a diverse set of challenges than the deep-rooted integration in logic processes. DRAM and flash memory, which consist of the greater part of the memory applications, demonstrate high aspect ratios, little critical dimensions, and high sensitivity to line resistance.

The development of the PVD market was strong for the acknowledgment of the copper barrier metal, which is characteristically a bi-layer of Ta/TaN, or TiN. Nevertheless, the evolution to memory has its own challenges. As characteristic size continues to reduce in size, a thinner barrier metal is requisite to capitalize on copper volume in the damascene structure and sustain efficient resistivity. Ultra-thin barrier metals must realize most favorable step coverage, density, and morphology in high aspect ratio trenches.