Euan Ramsay

Chromatic and spherical aberration correction for silicon aplanatic solid immersion lens for fault isolation and photon emission microscopy of integrated circuits

Current state-of-the-art in backside fault isolation and logic analysis utilizes solid immersion lens (SIL) imaging in the central configuration. An attractive advancement is the development and integration of an aplanatic SIL, which allows significant improvement in resolution, signal acquisition and isolation capabilities, especially for the 22 nm node and beyond. However, aplanatic SIL configurations introduce both chromatic and spherical aberrations. We have developed backing objective designs capable of correcting for chromatic aberrations allowing application in photon emission microscopy, as well as deformable mirror designs and experiments that eliminate spherical aberrations of aplanatic SILs to account for variations in substrate thickness and off-axis imaging.

Spherical aberration correction in aplanatic solid immersion lens imaging using a MEMS deformable mirror

Aplanatic solid immersion lens (SIL) microscopy is required to achieve the highest possible resolution for next generation silicon IC backside inspection and failure analysis. However, aplanatic SILs are very susceptible to spherical aberrations introduced by substrate thickness mismatch. We correct this aberration using a MEMS deformable mirror. Good agreement between theory and experiment is achieved and spot intensity increases by a factor of two to three are demonstrated.