Enhanced chemical etching and optical observation: a quality analysis technique for industrial SIMOX production

SIMOX is a well developed process for producing SOI materials. However, for some applications the top silicon layer still needs crystalline quality improvements. At present the density of threading dislocations on typical SIMOX materials (1.8x10¹⁸O⁺cm^-2) is about 10⁵cm^-2 for single implantation and about 10⁴ cm^-2 for multi-implantations. Due to the very small thickness of the top silicon layer a two step etching procedure using SECCO etching and bright field optical observations has been used to determine the dislocation density. A four step procedure which allows the transfer of the dislocation etch pits into the bulk was developed to increase the contrast between dislocation etch pits and the substrate. In this work, we describe an optimized enhanced chemical etching process. It allows etch pit observations using an optical microscope and automatic counting by the use of image processing software. This technique can be used for quality analysis and is "operator free"