Categories: Electronics

How scanning acoustic microscopy (SAM) aids hybrid bonding check

Hybrid bonding—a major development in chip packaging know-how—is changing into important in heterogeneous integration, which permits semiconductor firms to merge a number of chiplets with numerous capabilities, course of nodes, and sizes right into a unified bundle. It vertically hyperlinks die-to-wafer or wafer-to-wafer through intently spaced copper pads, bonding the dielectric and steel bond pads concurrently in a single bonding step.

Nonetheless, the improved reliability and mechanical energy of its interconnects in comparison with conventional bump-based interconnections don’t come with out challenges. As an example, to efficiently transition to high-volume manufacturing with excessive yields, it requires superior metrology instruments that may shortly determine defects comparable to cracks and voids inside the bonded layers.

PVA TePla OKOS, a Virginia-based producer of business ultrasonic non-destructive (NDT) methods, claims to have an answer based mostly on scanning acoustic microscopy (SAM). A non-invasive and non-destructive ultrasonic testing technique, SAM is shortly changing into the popular approach for testing and failure evaluation involving stacked dies or wafers, in keeping with Hari Polu, president of PVA TePla OKOS.

SAM makes use of ultrasound waves to non-destructively study inside constructions, interfaces, and surfaces of opaque substrates. The ensuing acoustic signatures will be constructed into 3D pictures which can be analyzed to detect and characterize system flaws comparable to cracks, delamination, inclusions, and voids in bonding interfaces. The pictures may also be used to guage soldering and different interface connections.

Determine 1 SAM is changing into a most popular approach for testing and failure evaluation involving stacked dies or wafers. Supply: PVA TePla OKOS

SAM—an business customary for inspection of semiconductor parts to determine defects comparable to voids, cracks, and delamination—has been tailored to facilitate 100% inspection of hybrid bonded packages, says Polu.

The way it works

In hybrid bonding, numerous steps have to be reliably carried out to make sure high quality. The method begins with manufacturing the wafers or dies in a semiconductor fab earlier than the chips are bonded collectively. The subsequent key steps embody the preparation and creation of the pre-bonding layers, the bonding course of itself, the post-bond anneal, and the related inspection and metrology at every of the step.

Nonetheless, in typical SAM methods, wafers are held horizontally in a chuck and processed in a water medium. That, in flip, might result in water ingress, which might trigger vital points within the subsequent step of meeting. Then again, by re-designing the chuck in a vertical orientation, engineers can use gravity to get rid of any concern over water ingress whereas additionally utilizing different water administration applied sciences.

Right here, SAM directs targeted sound from a transducer at a small level on a goal object. The sound hitting the article is both scattered, absorbed, mirrored, or transmitted. In consequence, the presence of a boundary or object and its distance will be decided by detecting the route of scattered pulses in addition to the time of flight. Subsequent, samples are scanned level by level and line by line to supply a picture.

Determine 2 SAM stands able to ship 100% non-destructive inspection of vertically stacked and bonded die-to-wafer or wafer-to-wafer packages to assist facilitate the adoption of hybrid bonding. Supply: PVA TePla OKOS

It’s essential to notice that scanning modes vary from single-layer views to tray scans and cross-sections and that multi-layer scans can embody as much as 50 unbiased layers. The method can extract depth-specific info and apply it to create 2D and 3D pictures. Then, the photographs are analyzed to detect and characterize flaws like cracks, delamination, and voids.

The AI enhance

Polu is assured that developments in synthetic intelligence (AI)-based evaluation of the info collected from SAM inspection of wafer-to-wafer hybrid bonding will additional automate high quality assurance and improve fab manufacturing. “Improvements within the design of wafer chucks, array transducers, and AI-based evaluation of inspection knowledge are converging to offer a extra sturdy SAM answer for fabs concerned in hybrid bonding,” he stated.

So, when fabs make the most of the upper degree of failure detection and evaluation, the manufacturing yield and general reliability of high-performance chips enhance considerably. “Each fab will finally transfer towards this degree of failure evaluation due to the extent of detection and precision required for hybrid bonding,” Polo concluded.

Particularly when the stakes are larger than ever as a result of one unhealthy wafer, die, or interconnection might trigger the whole bundle to be discarded down the road.

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The publish How scanning acoustic microscopy (SAM) aids hybrid bonding check appeared first on EDN.

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