Apparatus for physical vapor deposition and method for forming a layer

A ring, comprising:

• a ring body having a first top surface, a second top surface, a first bottom surface, a second bottom surface, an innermost sidewall coupled to the first top surface and the first bottom surface, an outermost sidewall coupled to the second top surface and the second bottom surface, the first bottom surface and the second bottom surface are parallel with each other, and the first bottom surface and the second bottom surface form a step height;
• a barrier structure disposed between the first top surface and the second top surface;
• and
• an insulating film over the barrier structure, wherein the first top surface and the second top surface of the ring body are free of the insulating film, and the insulating film comprises aluminum oxide or aluminum nitride,
• wherein the barrier structure comprises at least a first portion and a second portion,
• wherein the second portion is between the outermost sidewall and the first portion, the first portion and the second portion are separated by a first horizontal distance, a first vertical distance is defined between a top surface of the first portion and a top surface of the second portion, and the top surface of the second portion is higher than the top surface of the first portion, and
• wherein the top surface of the first portion of the barrier structure, the top surface of the second portion of the barrier structure and the first top surface of the ring body are higher than the second top surface of the ring body,
• wherein the insulating film over the first portion of the barrier structure entirely overlaps the first bottom surface, and
• wherein the insulating film is disposed over the first portion and the second portion of the barrier structure, and a lower surface of a first groove between the first portion and the second portion of the barrier structure is free of the insulating film.