Creation of Solid Immersion Lenses in Bulk Silicon Using Focused Ion Beam Backside Editing Techniques

Abstract

Abstract This work describes how Solid Immersion Lenses (SILs) can be created in bulk silicon using a focused ion beam and a bitmap milling process. The optical properties are in good agreement with the expected results for the achieved lens geometries. An improvement in lateral spatial resolution by a factor of 1.8 and in image contrast by 170 % for backside analysis is demonstrated. The presented SILs are 32 µm in diameter with a field of view of about 10 μm. This process can be an alternative when a regular SIL placement on the chip is impossible or complex. The advantages of this method are the use of a single kind of material (no air gaps and no additional lens material with different n value), the ability to precisely position the SIL on the circuitry and the fact that a SIL may be created in less than twenty minutes of processing time.