Apparatus and method for determining clamping status of semiconductor wafer

A method of ensuring that a semiconductor wafer is securely clamped to a support member before a semiconductor process is started, the method comprising:

• a) placing the semiconductor wafer in proximity to the support member;
• b) applying a force that tends to clamp the semiconductor wafer to the support member;
• c) measuring a degree by which the semiconductor wafer is clamped to the support member, to arrive at a determination of whether the semiconductor wafer is securely clamped to the support member, wherein the measuring step includes:
• 1) emitting ultrasonic energy toward an interface between the semiconductor wafer and the support member, so that echo signals are generated, the echo signals including a first intensity peak occurring at a first time;
• and
• 2) analyzing the echo signals for a second intensity peak occurring at a second time after the first time to determine whether the semiconductor wafer is securely clamped to the support member based on comparison of at least the second intensity peak to a threshold value;
• and
• d) based on the determination, either continuing with the semiconductor process or aborting the semiconductor process.

A method for verifying proper de-clamping of a semiconductor wafer from a support member before the semiconductor wafer is removed from the support member upon completion of a semiconductor process, the method comprising:

• a) releasing a force that tends to clamp the semiconductor wafer to the support member;
• b) measuring a degree by which the semiconductor wafer is clamped to the support member, to arrive at a determination of whether the semiconductor wafer is properly de-clamped from the support member, wherein the measuring step includes:
• 1) emitting ultrasonic energy toward an interface between the semiconductor wafer and the support member, so that the interface generates echo signals, the echo signals including a first intensity peak occurring at a first time;
• and
• 2) analyzing the echo signals for a second intensity peak occurring at a second time after the first time to determine whether the semiconductor wafer is properly de-clamped from the support member based on comparison of at least the second intensity peak to a threshold value;
• and
• c) if the determination indicates that the semiconductor wafer is properly de-clamped from the support member, physically removing the semiconductor wafer from the support member and continuing the semiconductor process on a subsequent semiconductor wafer.