Background

A metallic glass is a solid metallic material with a disordered structure at the atomic level. Because metallic glasses lack the crystalline lattice of metals, metallic glasses also lack the grain boundaries where metals’ lattice structure breaks down forming crystals. Without grain boundaries to deflect the flow of electrons, metal glasses show lower resistance and are less prone to electromigration at low film thicknesses ().

Technology Overview

The primary application for this technology is as a substitute material for the metallization layer in semiconductors. Metal layers had been Al. In the late 1990s, in partnership with Motorola, IBM developed a Cu interconnect technology with a lower resistivity. This technology is now reaching the end of its lifespan. As designers shift to multicore architectures to improve heat management in high-performance microprocessors, line resistance in long run, wire interconnects between cores is creating a bottleneck slowing information transfer between cores. High resistance and high capacitance in these wire interconnects require high power amplification to drive these loads. This creates reliability issues due to heat generation and electromigration. At present fully 50% of a chip’s power consumption occurs in such long wire interconnects. Long data, address, clock, and sensing wires in other semiconductor applications pose similar problems.

As semiconductor feature sizes shrink into the sub-10 nm range, previously ignored current interactions at the surface and grain boundaries of the metal polycrystal are further exacerbating these problems. For example, line resistivity in the transition from 30 nm processes to 10 nm processes increases by a factor of 10, more than triple the traditional rule of thumb. As the wire’s cross-section drops, the current density increases. Especially at grain boundaries, electrons interact more strongly with the lattice, disrupting flow and accelerating electromigration, the creation of atom-level gaps in the wire that eventually lead to wire malfunction. At sub-10 nm scales, interactions between electrons flowing in the line and grain boundaries are the principal mechanism for 1) greater power dissipation due to higher line resistance, and 2) lower interconnect reliability from electromigration.

Ag-Cu amorphous metallic glass addresses these challenges to interconnect performance. Composed of 40% Cu and 60% Ag, this metallic glass is deposited as a thin film in a high vacuum sputtering chamber. The inventors report that for a 10 nm Cu-Ag film, the resistivity is 2.82 x 10-7 ohms-cm, substantially lower than the resistivity for 10 nm Cu films. Enabling thin-film interconnections without grain boundaries, this metallic glass eliminates the principal source of increased line resistance and electromigration. Ag-Cu metallic glasses also have other advantageous characteristics such as low-temperature dependence, good mechanical properties, and good resistance to corrosion.

Stage of Development

Reduced to practice, and available for licensing

Benefits

Lower power dissipation in chip interconnect
Greater reliability of chip interconnect

Binary Ag-Cu Amorphous Thin Films for Electronic Applications

Patents

IP Status

Seeking