Scalable, sub 2μm pitch, Cu/SiCN to Cu/SiCN hybrid wafer-to-wafer bonding technology
This paper presents a novel approach to face-to-face wafer-to-wafer (W2W) bonding using SiCN-to-SiCN dielectric bonding, in combination with direct Cu-Cu bonding using Cu pads of unequal size and surface topography for the top and bottom wafers. The use of SiCN dielectrics allows to obtain a high W2W bonding energy (> 2 J/m2) at low annealing temperature (250 °C). Excellent Cu-Cu bonding is obtained after annealing at 350 °C. A novel CMP process, resulting in a slightly protruding Cu top pad and a slightly recessed Cu bottom pad, is introduced. The difference in pad sizes, allows for the necessary W2W overlay bonding tolerances. Excellent resistivity and yield results are obtained across bonded 300 mm Si wafers for scaled 360 nm top pads bonded to 720 nm bottom pads at 1.44 μm pitch (25% bottom Cu density). Feasibility of smaller pitches has been demonstrated by successfully bonding 180 nm top pads to 540 nm bottom pads at 0.72 μm pitch.
From PCB to BEOL: 3D X-Ray Microscopy for Advanced Semiconductor Packaging
X-ray imaging has been a key non-destructive analysis method for electronic packages and printed circuit boards (PCB) for over two decades. Applications such as artificial intelligence (AI), 5G, high-performance computing and internet-of-things (IOT) mandate higher IO density and 3D scaling at the device, package and system levels, thereby increasing the need for nondestructive imaging at high resolution and preferably in 3D. The first lab-based submicron X-ray microscopes (XRM) using focused-optics emerged in 2000 [1], based on components from synchrotron technology. This innovation enabled high-resolution 3D X-ray tomography on full packages. Since then a new type of XRM architecture in a lab-based instrument has emerged with spatial resolution in the tens of nanometers, when using a suitably prepared sample. When adopted in failure analysis (FA) workflows, submicron and nanoscale XRM enable successful failure analysis outcomes from PCB to die BEOL levels, even in complex samples. In addition, the unique capability to nondestructively acquire 3D images at high resolution is now driving the development of submicron XRM as a measurement solution offering rich 3D data and statistics to support advanced package development and manufacturing. XRM is continuing to grow in importance as the electronics industry develops more complex and integrated structures across all levels of the supply chain.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.