2 - Planar Inductive Sources

Abstract

This chapter reviews and describes the theoretical and practical aspects of operating a planar inductive plasma source. The next sections of the review discuss the theoretical and experimental aspects of the operation of planar inductive sources, followed by a discussion on the application of these sources to the etching of semiconductor materials. The wide range of applications for RF (Radiofrequency) driven, inductively driven plasma sources have been recently expanded even further due to the introduction of high density plasma sources in processing tools for the microelectronics industry. The trend in the microelectronics industry towards smaller circuit and device dimensions has led to stringent requirements on the rate at which processing occurs, the anisotropy of the process, and its selectivity. Selectivity generally occurs through a competition between chemical reactions and ion bombardment at the substrate surface. Thus it can be controlled by careful selection of the substrate voltage, the ion-to-neutral ratio, the feed gases, and by controlling the chemical reactions occurring within the plasma. In addition, certain applications require that the substrate not suffer any damage or contamination during processing that might degrade the electrical properties of the devices fabricated upon it. It is unclear, how well high density plasma sources meet this requirement but some initial research indicates encouraging results. A final requirement is that the process occurs uniformly over the material surface. The need for large area, uniform density plasma sources has led to cylindrical configurations where the diameter is much larger than the length. The planar inductive plasma source is the outcome of constructing an inductively driven plasma source with such geometry, and it has made an appearance in the commercial semiconductor etch equipment market. The review ends with a section on conclusions and an extrapolation of future developments of the planar inductive source.