Method for measuring wafer thickness

In combination,

• a pair of relatively movable vacuum chucks for engaging a wafer therebetween;
• at least one sensor for measuring the distance between said chucks and for emitting a first signal with said movable chuck in engagement with the other of said chucks and a second signal with said movable chuck in engagement with a wafer on the other of said chucks;
• and
• a calculator for determining a difference between said signals and emitting a corresponding signal as the thickness of the wafer.

A method of measuring the thickness of a wafer comprising the steps of

• measuring the distance between a first movable chuck when in engagement with a second rotatable chuck without a wafer therebetween and a fixed reference surface to establish a standard measurement value;
• thereafter placing a wafer on the second rotatable chuck and moving the first chuck into engagement with the wafer;
• measuring the distance between the first chuck when in engagement with the wafer and said fixed reference surface to obtain an actual measurement value;
• and
• calculating a difference between said actual measurement value and said standard measurement value as the thickness of the wafer.

A method of measuring the thickness of a wafer disposed between a pair of vacuum chucks, said method comprising the steps of measuring the distance between a first chuck of said chucks when in engagement with a second chuck of said chucks without a wafer therebetween and a fixed reference surface to establish a standard measurement value;

• thereafter placing a wafer on the second rotatable chuck and moving the first chuck into engagement with the wafer;
• measuring the distance between the first chuck when in engagement with the wafer and said fixed reference surface to obtain an actual measurement value;
• and
• comparing said actual measurement value and said standard measurement value to obtain a difference therebetween as the thickness of the wafer.

An apparatus for measuring a thickness of a wafer without contacting the wafer, said apparatus comprising;

• a pair of relatively movable vacuum chucks for engaging a wafer therebetween;
• at least one sensor for measuring the distance between a movable one of said chucks when in engagement with the wafer and a fixed reference surface to establish an actual measurement value, said sensor being spaced from a wafer engaged between said chucks;
• and
• a calculator for determining a difference between said actual measurement value and a standard measurement value as the thickness of the wafer.

A method of measuring the thickness of a wafer in a contact less manner comprising the steps of measuring the distance between a first movable chuck when in engagement with a second rotatable chuck without a wafer therebetween and a fixed reference surface to establish a standard measurement value;

• thereafter placing a wafer on the second rotatable chuck and moving the first chuck into engagement with the wafer;
• measuring the distance between the first chuck when in engagement with the wafer and said fixed reference surface to obtain an actual measurement value without contacting the wafer between the chucks;
• and
• calculating a difference between said actual measurement value and said standard measurement value as the thickness of the wafer.