The theoretical fundamentals of diffractive solid immersion lenses (dSILs) were revised and adapted to a new application: the direct single-step chemistry-assisted creation of binary dSILs in silicon with a focused ion beam (FIB). Current results were able to prove the general functionality of this technique, but also showed the limitations still present. These limitations were identified; the underlying problems were analyzed and were addressed by optimizing several aspects of the process. The presented dSIL has a diameter of 150 ìm and is created in 15 minutes of processing time. It is designed for a sample thickness of 70 µm, which can be well adjusted if needed. For this sample thickness, the theoretical numerical aperture is about 2.5, offering a significant improvement in resolution. Furthermore a comparison of diffractive and refractive solid immersion lenses is presented, both created in a similar process. Apart from general aspects of dSILs and rSILs (refractive SILs), details of the designs presented in this work are compared. This leads to the insight of which method (dSIL or rSIL) has its advantages for which type of application.