Thermal hillocks on half-micron aluminum lines: the next reliability issue?

Thermally induced Al hillocks cause manufacturing and reliability problems in integrated devices. These thermal hillocks, which form during the sinter process, interfere with the uniformity of subsequent spin-on materials (e.g. photoresist) and can create pinholes susceptible to corrosion or electrical breakdown. Thermal hillocks have both lateral and vertical dimensions on the order of 1 μm. The authors find that thermal hillocks are present on lines having linewidths greater than 3 μm, absent on lines having linewidths between 0.8 μm and 3 μm, and, again, present on lines having linewidths of 0.6 μm. These last hillocks are defined as line hillocks to distinguish them from hillocks occurring in the wider areas