Laser Induced Stress Wave Thermometry for In-Situ Temperature and Thickness Characterization of Single Crystalline Silicon Wafer Part II – Experimental Results

TAP-NDE is employed to perform an experimental study on silicon wafers of different thicknesses to determine the maximum possible resolution of TAP-NDE towards temperature sensitivity, and to demonstrate the ability to differentiate between wafers of different deposition layer thickness at temperatures up to 600°C. Temperature resolution is demonstrated for ±10°C resolution and for ±5°C resolution; while thickness differentiation is carried out with wafers carrying 4,000 Å and 8,000 Å of aluminum deposition layer. The experimental group velocities of a set of selected frequency components extracted using the Gabor wavelet time-frequency analysis compare favorably to their corresponding theoretical group velocities. It is shown that TAP-NDE is a feasible tool for identifying and characterizing thickness and temperature changes simultaneously during thermal annealing that can replace the current need for separate characterization of these two important parameters in semiconductor fabrication.