Decoration and preferential etching of crystal defects in silicon materials: influence of metal decoration on the defect etching process

Delineation of crystal defects in SOI wafers can be accomplished by preferential etching with solutions such as dilute Secco etch. By application of decoration procedures with metals such as copper or lithium delineation of defects by preferential etching can be improved due to acceleration of the etching process at the metal decorated defects. Parameters such as removal rate, selectivity and activation energy for the etching process are used to describe the influence of metal decoration on preferential etching of defects in SOI wafers. In this work the selectivity of a dilute Secco etch was determined experimentally on dislocations generated by damaging silicon substrates by indentation with a diamond tip and subsequent annealing at 1000 °C. After dilute Secco etching the depth of the dislocation etch pits was measured by an atomic force microscope. Both the selectivity and the activation energy were compared for non-decorated and copper or lithium decorated samples of SOI wafers or silicon substrates. Typical values obtained for activation energies of non-decorated samples were 29-33 kJ/mol, those of decorated samples were in the range of 25-34 kJ/mol. For the selectivity the values for non-decorated samples were about 1.95 and increased with the level of copper decoration up to 3.0. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)