Abstract: Disclosed is a method and apparatus for measuring semiconductor substrate temperature using a differential acoustic time of flight measurement technique. The measurement is based on measuring the time of flight of acoustic (ultrasonic) waves across the substrate, and calculating a substrate temperature from the measured time of flight and the known temperature dependence of the speed of sound for the substrate material. The differential acoustic time of flight method eliminates most sources of interference and error, for example due to varying coupling between an ultrasonic transducer and the substrate. To further increase the accuracy of the differential acoustic time of flight measurement, a correlation waveform processing algorithm is utilized to obtain a differential acoustic time of flight measurement from two measured ultrasonic waveforms. To facilitate signal recognition and processing, a symmetric Lamb mode may be used as mode of excitation of the substrate.

Abstract: Disclosed is a method and apparatus for measuring semiconductor substrate temperature using a differential acoustic time of flight measurement technique. The measurement is based on measuring the time of flight of acoustic (ultrasonic) waves across the substrate, and calculating a substrate temperature from the measured time of flight and the known temperature dependence of the speed of sound for the substrate material. The differential acoustic time of flight method eliminates most sources of interference and error, for example due to varying coupling between an ultrasonic transducer and the substrate. To further increase the accuracy of the differential acoustic time of flight measurement, a correlation waveform processing algorithm is utilized to obtain a differential acoustic time of flight measurement from two measured ultrasonic waveforms. To facilitate signal recognition and processing, a symmetric Lamb mode may be used as mode of excitation of the substrate.