G - Physics – 01 – N
Patent
G - Physics
01
N
G01N 21/71 (2006.01) G01N 25/18 (2006.01) G01N 25/20 (2006.01) G01R 31/265 (2006.01) H01L 21/66 (2006.01)
Patent
CA 2126481
There is provided a method of measuring thermal diffusivity of solids and electronic lifetimes and defect properties of semiconductors useful for in-situ, non- destructive monitoring of engineered materials and electronic substrates. The method, termed photothermal rate window method, involves irradiating a sample with a repetitive square laser pulse of duration Tp and period T0 and monitoring the temperature profile by measuring the photothermal signal emitted from the sample. The period T0 of the repetitive heating pulse is maintained constant and the pulse duration Tp is varied in the range between 0 and T0 with the temperature measured at each value of Tp. The method of measuring semiconductor recombination lifetimes involves irradiating a sample and scanning one of either the period T0 and the pulse duration Tp of the repetitive laser pulse with the other held constant. The photothermal signal emitted from the surface is measured. Defect energy states in semiconductors are measured by irradiating the sample with a repetitive laser pulse of duration Tp and period T0 (both fixed) and monitoring the photothermal signal as the sample temperature is scanned. Defect levels are correlated with extremum in the profile. The photothermal signal in all the foregoing methods is input into a lock-in amplifier which measures the fundamental Fourier component of the signal. The output of the lock-in amplifier is fitted to a theoretical model of the photothermal response of a repetitively irradiated sample to obtain the thermal diffusivity, or the recombination lifetime.
Mandelis Andreas
Munidasa Mahendra
Wolff Detlev
Mandelis Andreas
Munidasa Mahendra
Photo-Thermal Diagnostics Inc.
Schumacher Lynn C.
Wolff Detlev
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