Retaining ring for chemical-mechanical polishing

A chemical-mechanical polishing apparatus, comprising:

• a polishing pad;
• a polishing head configured to receive a wafer and to hold the wafer against the polishing pad;
• and
• a retaining ring configured to engage with the polishing head, wherein the retaining ring comprises:
• an annular wall having an outer surface and an inner surface;
• and
• a channel extending from the outer surface to the inner surface, wherein the channel includes baffles positioned within the channel to reduce a cross-sectional flow area of the channel, wherein the baffles are arranged periodically along a length of the channel.

A chemical-mechanical polishing apparatus, comprising:

• a polishing pad;
• a polishing head configured to receive a wafer and to hold the wafer against the polishing pad;
• and
• a retaining ring configured to engage with the polishing head, wherein the retaining ring comprises:
• an annular wall encircling the wafer and having an outer surface and an inner surface;
• and
• a channel extending from the outer surface to the inner surface, wherein the channel extends in a curvilinear direction, wherein the channel is defined by an inner wall of the retaining ring, wherein the channel includes a protrusion extending from the inner wall of the channel into a flow path defined by the channel, wherein the flow path has an upstream cross-sectional flow area immediately upstream of the protrusion and a downstream cross-sectional flow area immediately downstream of the protrusion, and wherein the upstream cross-sectional flow area and the downstream cross-sectional flow area are equal.