Axiomatic Design of a Chemical Mechanical Polishing (CMP) Wafer Carrier With Zoned Pressure Control

Axiomatic Design was used to develop a complete platform for chemical mechanical polishing (CMP) of silicon wafers. A functional requirement of the machine emerging from the axiomatic design process is the control of the wafer-scale polishing uniformity. Mechanisms to maintain control of the uniformity were designed, and integrated into a wafer carrier, which holds the wafer during polishing and applies normal pressure to the polishing interface. The wafer carrier is capable of controlling the pressure in four annular zones on a 200 mm wafer, as well as the pressure of the surrounding retaining ring. Initial testing of the wafer carrier indicates a successful design, offering removal non-uniformity of 1.7% after polishing 5,700 Å of SiO₂ from the surface of a silicon wafer.