VAF Instruments (Netherlands)

Pitch scaling of interconnects is required for 3D system integration with the industry shifting to bumpless bonding technology. However, hybrid metal/dielectric bonding requires tight process control of planarity after chemical mechanical polishing (CMP) to avoid bonding voids. Due to its sub-angstrom resolution, atomic force microscopy (AFM) is typically used to assess the nano-topography but conventional systems suffer from increased noise floor at high scanning speeds making it unsuitable for high-volume manufacturing (HVM). Here, we validate a novel in-line high-throughput AFM system (QUADRA) by reporting the topographical parameters of 250 nm and 1 μm size copper nano-pads at high scanning speeds that reach tens of wafers per hour throughput.

We have developed a model-based, parallel procedure to estimate fluorescence lifetimes. Multiple frequencies are present in the excitation signal. Modeling the entire fluorescence and measurement process produces an analytical ratio of polynomials in the lifetime variable τ. A non-linear model-fitting procedure is then used to estimate τ. We have analyzed this model-based approach by simulating a 10 μM fluorescein solution (τ = 4 ns) and all relevant noise sources. We have used real LED data to drive the simulation. Using 240 μs of data, we estimate τ = 3.99 ns. Preliminary experiments on real fluorescent images taken from fluorescein solutions (measured τ = 4.1 ns), green plastic test slides (measured τ = 3.0 ns), and GFP in U2OS (osteosarcoma) cells (measured τ = 2.1 ns) demonstrate that this model-based measurement technique works.