Isolator apparatus and methods for substrate processing chambers

An isolator ring for a substrate processing chamber, the isolator ring comprising:

• an annular member including:
• a first surface facing radially inwardly;
• a protrusion that protrudes radially inwardly from the first surface;
• and
• a second surface facing radially outwardly;
• wherein in use:
• the first surface faces a pedestal of the substrate processing chamber, the first surface disposed at a gap from an outer circumferential surface of the pedestal;
• the protrusion defines a necked portion of the gap between the pedestal and the first surface, and defines a stepped surface;
• the gap between the first surface and the outer circumferential surface of the pedestal has a first width;
• the necked portion between the stepped surface and the outer circumferential surface of the pedestal has a second width smaller than first width;
• and
• the second width is a ratio of the first width, the ratio within a range of 0.25 to 0.75.

An isolator ring for a substrate processing chamber, the isolator ring comprising:

• an annular member including:
• a first surface facing radially inwardly;
• a second surface facing radially outwardly;
• and
• an upper surface tapering upwards in a direction from the second surface and towards the first surface, and defining an upper edge;
• wherein in use:
• the upper edge is disposed above a support surface of a pedestal in the substrate processing chamber;
• the upper edge is disposed at a distance from a lower surface of a showerhead of the substrate processing chamber;
• the support surface of the pedestal is disposed at a gap from the lower surface of the showerhead;
• and
• the distance is within a range of 50 percent to 100 percent of the gap.