Sub-Band Absorption Spectrum of Defects in Silicon Wafers Using Thermo-Reflectance Spectroscopy
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
This non-contact and non-destructive instrument provides quantitative evaluation and characterization of defect areas (5-10 mm2) in Si wafers within a depth of 10-20 mm, and identification of contaminants. To characterize defects in Si wafers in a completely non-contact and non-destructive manner, it is most convenient to observe optical absorption for incident energies below the fundamental band-to-band absorption edge. A sub-band absorption spectrum provides information on the energy levels of defects in Si wafers. It is difficult, by conventional absorption techniques, to obtain a subgap absorption spectrum for an individual defect area as small as 5-10 mm to a depth of 10-20 mm below the Si surface. This instrument uses optically induced thermo-reflectance.