Solid Immersion Lens (SIL) objectives are used to increase the numerical aperture (NA) of an optical system to increase the resolution; therefore, enabling the user to see smaller IC geometries. Additionally, the higher the NA derived from a SIL improves the collection efficiency of the system.
Checkpoint has designed and built SIL’s for the FA and debugging market for 10+ years. By using its proprietary backing object designs, Checkpoint has been able to lead the market in SIL development. The design of all of Checkpoint’s SIL’s is that of a hemispherical SIL tip. This design allows the user to use the same SIL objective for multiple wavelengths and a range of DUT thicknesses. Also, since Checkpoint assembles and polishes its own SIL tips, SIL objectives are available in both Si and GaAs and are customizable for almost any Si IC thickness.
Checkpoint’s latest SIL with an NA of 3.3 and using a 1064 laser is capable of resolving structures below 220 nm. Figure 1 is an image of a SIL imaging a resolution structure of 240 nm pitch.