Apparatus and method for sputter depositing dielectric films on a substrate

An apparatus for sputter depositing a layer of material on a substrate comprising:

• a sputtering chamber having an internal conductive wall which defines a processing space;
• a substrate mount positioned in the processing space for supporting a substrate therein;
• a sputter target positioned in the processing space opposite said substrate mount;
• a power source for biasing the target and exciting a process gas introduced in the processing space into a plasma such that the plasma sputters material from the target and the sputter material deposits on a substrate supported on said substrate mount and on a surface of the chamber wall to form respective material layers thereon, a surface of the chamber wall operable for providing an electrical reference for the plasma during sputter deposition;
• a conductive shield positioned in the processing space between the target mount and the substrate mount and configured for capturing a portion of the sputtered material which would otherwise deposit on the chamber wall surface during sputter deposition, the shield having a surface operable for providing another electrical reference for the plasma;
• a source of ground potential coupled to the conductive shield and chamber wall for maintaining said shield and wall as a ground reference;
• the conductive shield operable for reducing the amount of sputtered material which deposits on a portion of the chamber wall surface and maintaining said chamber wall surface portion as a generally stable ground reference for the plasma, and further including a plurality of apertures formed therein, the apertures comprising a cumulative area in the range of approximately 10% to 50% of the area of an inner surface of the shield for being operable for passing plasma therethrough during sputter deposition to contact said shield and wall ground references;
• at least one of the shield apertures having at least one dimension in the range of approximately 0.25 to 2.0 times the mean free path length of a process gas to be introduced into the chamber;
• whereby a stable and continuous sputter deposition process may be achieved.

A method for sputter depositing a layer of material on a substrate comprising:

• providing a sputtering chamber having an internal conductive wall which defines a processing space;
• positioning a substrate in the processing space;
• positioning a sputter target in the processing space opposite said substrate;
• biasing the target and exciting a process gas introduced in the processing space into a plasma such that the plasma sputters material from the target and the sputter material deposits on the substrate and on the chamber wall to form respective material layers thereon, a surface of the chamber wall providing an electrical reference for the plasma during sputter deposition;
• positioning a conductive shield between the target and substrate for capturing an amount of the sputtered material to reduce the amount of sputtered material which otherwise deposits on a portion of the chamber wall surface and maintaining said chamber wall surface portion as a generally stable electrical reference for the plasma;
• the shield including a plurality of apertures comprising a cumulative area in the range of approximately 10% to 50% of the area of an inner surface of the shield;
• the process gas having particles with a predetermined mean free path length and at least one of the shield apertures having at least one dimension in the range of approximately 0.25 to 2.0 times the mean free path length of a process gas introduced into the chamber;
• passing plasma through the apertures and to the stable electrical reference for maintaining a stable plasma;
• coupling the conductive shield to a source of ground potential for grounding the shield during sputter deposition;
• whereby a stable and continuous sputter deposition process may be achieved.