Contactless capacitive measurement tool with improved throughput and accuracy

A metrology tool for measuring wafer bow, the metrology tool comprising:

• a wafer mount configured to support a semiconductor wafer;
• a bar-shaped capacitive sensor unit including:
• a sensor housing having a first surface, the first surface facing a surface of the semiconductor wafer when the bar-shaped capacitive sensor unit is in close proximity to the semiconductor wafer;
• and
• a plurality of electrodes provided on the first surface of the sensor housing and arranged in a line along a length of the sensor housing, wherein each electrode works in conjunction with a corresponding opposing area on the surface of the semiconductor wafer to form a capacitor with:
• (a) the electrode forming a top plate of the capacitor, and (b) the corresponding opposing area on the surface of the semiconductor wafer forming a bottom plate of the capacitor;
• a movement device configured to move at least one of the wafer mount and the bar-shaped capacitive sensor unit relative to each other;
• and
• a controller configured to:
• (a) obtain a plurality of capacitance values from the plurality of electrodes by measuring a capacitance between each electrode and the corresponding opposing area on the surface of the semiconductor wafer, (b) calculate a distance between each electrode and the corresponding opposing area of the surface of the semiconductor wafer based on the capacitance value measured at the electrode, and (c) determine a bow of the semiconductor wafer based on the calculated distances.

A method of measuring wafer bow, the method comprising:

• positioning a capacitive sensor unit in close proximity to a semiconductor wafer, the capacitive sensor unit comprising a sensor housing and a plurality of electrodes, each electrode facing a corresponding opposing area on a surface of the semiconductor wafer, such that the electrode and the corresponding opposing area form a capacitor;
• moving the capacitive sensor unit across the surface of the semiconductor wafer;
• obtaining a plurality of capacitance values from the plurality of electrodes by measuring a capacitance between each electrode and the corresponding opposing area on the surface of the semiconductor wafer as the capacitive sensor unit moves across the surface of the semiconductor wafer;
• calculating a distance between each electrode and the corresponding opposing area of the surface of the semiconductor wafer based on the capacitance value measured at the electrode;
• and
• determining a bow of the semiconductor wafer based on the calculated distances.