Closed-loop control of wafer polishing in a chemical mechanical polishing system

A chemical mechanical polishing system comprising:

• a wafer polishing surface;
• a carrier head for holding a wafer, wherein the carrier head includes one or mare chambers and being operable, by adjusting pressure in at least one of the one or more chambers, to change a force applied to the backside of the wafer, a loading area on the backside of the wafer where the force is applied, or both the force and the loading area;
• a monitor for obtaining thickness-related measurements of the wafer during polishing;
• memory that stores a target thickness profile;
• and
• a processor configured to:
• (a) calculate a thickness profile for the wafer based on a thickness-related profile obtained by the monitor;
• (b) compare the calculated thickness profile to a target thickness profile;
• and
• (c) define, based on a result of the comparison, a recipe specifying a first set of pressure values for applying a first force to a first loading area, and a second set of pressure values for applying a second force to a second loading area, a first time interval during which the one or more chambers are pressurized in accordance with the first set of pressure values, and a second time interval during which the one or more chambers are pressurized in accordance with the second set of pressure values, each pressure value of a set representing the pressure at which a respective one of the one or more chambers is pressurized, wherein pressurizing the one or more chambers in accordance with the recipe during polishing results in a thickness profile that is more similar to the target profile than was the calculated thickness profile.

An article comprising a computer-readable medium that stores computer-executable instructions for causing a polishing apparatus to:

• cause a carrier bead to hold a wafer that includes a front side and a backside, the carrier head including one or more chambers and being operable, by adjusting pressure in at least one of the one or more chambers, to change a force applied to the backside of the wafer, a loading area on the backside of the wafer where the force is applied, or both the force and the loading area;
• polish the front side of the wafer by holding the wafer against a polishing surface;
• obtain thickness-related measurements of a wafer during polishing;
• calculate a thickness profile for the wafer based on the thickness-related measurements;
• compare the calculated thickness profile to a target thickness profile;
• and
• define, based on a result of the comparison, a recipe specifying a first set of pressure values for applying a first force to a first loading area, and a second set of pressure values for applying a second force to a second loading area, a first time interval during which the one or more chambers are pressurized in accordance with the first set of pressure values, and a second time interval during which the one or more chambers are pressurized in accordance with the second set of pressure values, each pressure value of a set representing the pressure at which a respective one of the one or more chambers is pressurized, wherein pressurizing the one or more chambers in accordance with the recipe during polishing results in a thickness profile that is more similar to the target profile than was the calculated thickness profile.