Method and apparatus for improving sidewall coverage during sputtering in a chamber having an inductively coupled plasma

Abstract

Increased sidewall coverage by a sputtered material is achieved by generating an ionizing plasma in a relatively low pressure sputtering gas. By reducing the pressure of the sputtering gas, it is believed that the ionization rate of the deposition material passing through the plasma is correspondingly reduced which in turn is believed to increase the sidewall coverage by the underlayer. Although the ionization rate is decreased, sufficient bottom coverage of the by the material is maintained. In an alternative embodiment, increased sidewall coverage by the material may be achieved even in a high density plasma chamber by generating the high density plasma only during an initial portion of the material deposition. Once good bottom coverage has been achieved, the RF power to the coil generating the high density plasma may be turned off entirely and the remainder of the deposition conducted without the high density plasma. Consequently, it has been found that good sidewall coverage is achieved in the latter part of the deposition.

Description

FIELD OF THE INVENTION [0001] The present invention relates to plasma generators, and more particularly, to a method and apparatus for generating a plasma to sputter deposit a layer of material in the fabrication of semiconductor devices. BACKGROUND OF THE INVENTION [0002] Low pressure radio frequency (RF) generated plasmas have become convenient sources of energetic ions and activated atoms which can be employed in a variety of semiconductor device fabrication processes including surface treatments, depositions, and etching processes. For example, to deposit materials onto a semiconductor wafer using a sputter deposition process, a plasma is produced in the vicinity of a sputter target material which is negatively biased. Ions created adjacent the target impact the surface of the target to dislodge, i.e., “sputter” material from the target. The sputtered materials are then transported and deposited on the surface of the semiconductor wafer. [0003] Sputtered material has a tendency ...

AI Technical Summary

Benefits of technology

This approach significantly reduces the formation of voids by improving sidewall coverage of underlayers, facilitating better interaction with subsequent overlayer materials and reducing the incidence of undesirable cavities in the deposition layer.

Problems solved by technology

As a consequence, materials deposited in etched openings including trenches and holes of semiconductor devices having openings with a high depth to width aspect ratio, may not adequately coat the walls of the openings, particularly the bottom walls.

If a large amount of material is being deposited, the deposited material can bridge over causing undesirable cavities in the deposition layer.

However, material sputtered by a low density plasma often has an ionization degree of less than 10% which is usually insufficient to avoid the formation of an excessive number of cavities.

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