Ionized-PVD by pulsed sputtering of Ta for metallization of high-aspect-ratio structures in VLSI

Abstract

Ionized metal deposition can be obtained from a magnetron source when using a pulsed power supply with extremely high power in the pulses. We have used peak power densities of several kW cm/sup -2/ with a repetition frequency of 50 Hz. To avoid overheating of the larger and the magnetron, a duty factor of less than 1% was used. The pulsed sputtering technique was employed for deposition of Ta thin films. The sputtering results in a very dense plasma with the ionized fraction of the deposited Ta flux arriving at a substrate (50 cm away from the source) estimated to be 60% or more (for P/sub Ar/=0.13 Pa and pulse energies /spl ges/6 J). This should be compared to normal dc sputtering where the degree of ionization could not be detected (<5%). This pulsed sputtering technique has a great potential for many industrial applications. One example is front-end metallization integrated circuits with high-aspect-ratio structures.