Backside sample preparation with laser-enhanced chemical etching for infrared photon imaging

Backside sample preparation has been widely used in failure analysis of integrated circuits (IC). Conventional backside sample preparation methodologies include mechanical grinding, parallel polishing, chemical etching with mask, etc. The mechanical grinding or polishing could induce mechanical damage in the Si. Normally the thickness after sample preparation with mechanical methods is about 100 urn and above. Chemical etching can be applied to get thinner sample, e.g., less than 30 um and below. For a sample with thickness less than 30 urn, mechanical support is needed. In order to make selective etching on substrates, a patterned mask has to be applied on the sample. In this paper, we will present a new methodology for backside sample preparation, which uses laser-enhanced chemical etching to open a trench on Si from the backside. This methodology can get thinner backside sample with strong mechanical support from the substrate.