Performance of Forming Substrate into Solid Immersion Lens (FOSSIL) for Backside Fault Isolation Techniques

摘要

Conventional backside fault isolation techniques take advantage of silicon's transmission of near-infrared (IR) light with energies less than silicon's bandgap energy, namely, wavelengths greater than 1 μm. However, the lateral spatial resolution of those techniques is limited by diffraction to approximately half the wavelength, and the resolution with an IR laser of λ = 1.3μm, which is generally used for backside fault isolation, is actually approximately 1 μm. On the other hand, 90 nm node devices currently in development require high resolution that is clearly beyond the capability of conventional backside fault isolation techniques. In the 90 nm node devices, the minimum pitch of gate and metal features is approximately 0.4 and 0.25μm, respectively. For this technology, a resolution of less than 0.25μm is necessary to identify failure points in transistors or metal lines.