Page 12 - Chip Scale Review_November-December_2023-digital
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Figure 6: SAM images of defective bonding (delamination and voiding) caused by surface particles.
Figure 7: Automatic optical inspection (AOI) of the a) surface and b) sidewall of singulated dies of a tape-frame wafer after thinning and the saw-dicing process. A
large number of particles (black) can be seen adhering to the sidewall. c-d) An incorrect further cleaning detaches and redeposits the particles onto the die surface. c-e)
The organic nature of the particles revealed by energy-dispersive X-ray spectroscopy inspection suggests tape adhesive as the origin. If not properly removed, f) these
particles can cause die delamination after bonding, as seen under SAM inspection.
normal quantile plot in Figure 8c, which yield impact of queue time between the variance increases with a more complex
shows a >99.5% continuity electrical test various process steps, as batch-mode bonding configuration, where >3-5 different
yield (a significant improvement from processing makes it difficult to control chiplets are in the roadmap to be bonded to
pre-optimization data). The process queue time. Samples were processed with the same substrate. Three bonded wafers
improvement was reflected in overall mean a 36-hour queue time and compared with from the “delayed” lot were compared to
resistance and variability. the baseline; in the high-volume production the baseline in Figure 9. Adding queue
The same test vehicle was further used to case, one could expect a queue time of 1 time leads to significantly lower yield (80%)
characterize the process-induced possible to 2 days, and not just time, but also its vs. the reference case (98%).
Figure 8: Post optimization: a) CSAM result showing void-free bonding, b) a wafer contour plot of 10,000-connectivity daisy-chains resistance, and c) Normal-quantile
plot of 10,000 connectivity DC showing >99.5% yield (~230-dies)—a significant improvement from pre-process optimization.
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10 Chip Scale Review November • December • 2023 [ChipScaleReview.com]
