Method and apparatus for low pressure sputtering

Abstract

Sputtering processes are carried out at low pressure, of less than one milli-Torr, particularly in the range of 0.05 to 0.5 mTorr, to reduce scattering of the sputtered particles due to collisions with atoms of the process gas, particularly for coating contacts at the bottoms of sub-micron sized holes of high aspect ratios. The sputtering is made possible by provision for a supplemental RF plasma generating source by which RF energy is reactively coupled into the gas within the chamber in close proximity to the surface of a sputtering target, preferably adjacent the periphery thereof. The pressure in the chamber as well as the power to an RF electrode by which the supplemental plasma is energized and the DC power by which the main target is energized are dynamically controlled so that the plasma is sustained at low pressure. First, the pressure in the chamber is raised to above 1 mTorr while the RF power on the supplemental electrode is applied to ignite the plasma, then this RF power is reduced and DC power on the target is increased to an operating level, whereupon the pressure in the chamber is reduced to below 1 mTorr for the low pressure sputtering of the wafer.

Dependencies are inferred from the claim text.