IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Monday Sessions
       Session PS-MoP

Paper PS-MoP4
Controllable Ion Source for Process Enhancement in a Downstream Plasma Ash Chamber

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Plasma Diagnostics and Plasma-Surface Interactions Poster Session
Presenter: A.K. Srivastava, Axcelis Technologies, Inc.
Authors: A.K. Srivastava, Axcelis Technologies, Inc.
P. Sakthivel, Axcelis Technologies, Inc.
I. Berry, Axcelis Technologies, Inc.
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
Plasma ash tools have in the past been designed to generate a gentle downstream plasma impinging on the wafer. However, additional demands to remove residue, both in front-end and back-end processes have recently been imposed on these ash tools. This has led to a gradual transition of the old plasma asher into a ash-etch hybrid tool that can tolerate harsh etchants in moderate amounts, and also have the flexibility of controlling the ion flux to the wafer without charge damage. Different approaches have been attempted to meet these needs with limited success, mostly by taking the chamber towards the reactive ion etch (RIE) regime where the risk of device damage is high. A new approach to the dynamic control of ion generation and transport to the wafer, while maintaining operating regimes that are conducive to an ash tool and hence non-destructive to the wafer, is reported in this paper. In a typical downstream plasma ash tool, an upstream microwave discharge is fed into a plenum that disperses the reactive species through a hard-coated aluminum baffle plate above the wafer. When ion bombardment is required, a secondary ion source coupling radio frequency (RF) is switched on, creating a glow discharge in the plenum above the baffle plate. Under optimal conditions, electrons from the glow discharge are trapped inside the sheath of the baffle plate holes. These electrons complete the current path on the bottom surface of the baffle plate, and have sufficient energy to ionize some of the neutral gas. This secondary source of ions provides a gentle, low energy, uniform bombardment on the wafer. This paper describes the ion source in detail as it is used during specific ash/residue removal processes. The unique ion generation mechanism is discussed. Preliminary results of ion bombardment on the removal of the carbonized layer of implanted resist at low temperature are presented. Optical emissions data characterizing the ash chemistries are also presented.