Characterization of ultra thin SOI and SSOI substrates: Defect and strain analysis

Two SOI substrate characterization procedures which need to be established for sub-500 Å Si thickness and strained SOI technology (or both) are crystal defect analysis and lattice strain measurement. Crystal defect detection using chemical etching is investigated for use on SOI substrates with a top Si layer thickness below 500 Å. A SSOI layer is used to measure the ratio of the defect site etch rate to that of the non-defective crystal for three popular Si defect etch chemistries: Secco, Schimmel and Wright-Jenkins. It is shown that defects are etched approximately three times faster than the surrounding crystal in Secco solution, compared to only about two times faster in either Schimmel or Wright-Jenkins solution. A comparison of the Si lattice strain measured by X-ray diffraction, transmission electron microscopy (moirè analysis) and Raman spectroscopy is presented.