The LaserFIB: new application opportunities combining a high-performance FIB-SEM with femtosecond laser processing in an integrated second chamber

Abstract

The development of the femtosecond laser (fs laser) with its ability to provide extremely rapid athermal ablation of materials has initiated a renaissance in materials science. Sample milling rates for the fs laser are orders of magnitude greater than that of traditional focused ion beam (FIB) sources currently used. In combination with minimal surface post-processing requirements, this technology is proving to be a game changer for materials research. The development of a femtosecond laser attached to a focused ion beam scanning electron microscope (LaserFIB) enables numerous new capabilities, including access to deeply buried structures as well as the production of extremely large trenches, cross sections, pillars and TEM H-bars, all while preserving microstructure and avoiding or reducing FIB polishing. Several high impact applications are now possible due to this technology in the fields of crystallography, electronics, mechanical engineering, battery research and materials sample preparation. This review article summarizes the current opportunities for this new technology focusing on the materials science megatrends of engineering materials, energy materials and electronics.

Keywords: Crossbeam laser; Dual chamber SEM; FIB-SEM; Femtosecond laser; LaserFIB; PFIB.

Fig. 1

Schematic layout of the fs laser chamber with principal components outlined

Fig. 2

Direct observation of a large 3D structure produced from direct fs laser ablation. The surface of the sample shows some minor repeating structures called LIPSS. Such 3D structures can then be used as a starting point for high resolution 3D tomography or EBSD using standard FIB-SEM workflows

Fig. 3

EBSD grain map overlaid on laser milled surface of a copper sample. The laser milled surface is sufficient to produce adequate indexing to enable EBSD mapping

Fig. 4

Scanning electron micrograph of a WC island milled into a bulk sample surface. The island is 180 μm on wide and 120 μm high and was milled in 85 s using the ZEISS Crossbeam Laser

Fig. 5

Micropillar of nuclear grade graphite prepared using the fs laser ablation attachment of the ZEISS Crossbeam. The pillar protrudes 250 μm above the sample surface of a ~ 1 mm² bulk sample. The laser milling time was 750 s

Fig. 6

3D X-ray image of a < 1 mm field-of-view of package interconnect structures within an AMD Vega64 2.5D package. Acquired with ZEISS Xradia 620 Versa using 0.7 μm voxel size

Fig. 7

Results of fs-laser ablation of glass processed in 651 and 96 s, respectively

Fig. 8

SEM cross-sectional image of a 14 nm silicon node 3D flip chip package immediately after laser polishing, without any ion beam clean-up

Fig. 9

a Delamination due to mechanical stress of the active layer of an OLED display - the organic layer and thin-film transistor are found 300 μm below the surface of the device, with 20 s of laser milling. b Electrodes of the thin-film transistor layer of a commercial OLED device, after 40 s of very low power fine polishing with the fs-laser. c Electrodes of the thin-film transistor layer of a commercial OLED display, after FIB polishing for 10 min