Mitigating Surface Damage Of Probe Pads In Preparation For Direct Bonding Of A Substrate
Patent No. US11978681 (titled "Mitigating Surface Damage Of Probe Pads In Preparation For Direct Bonding Of A Substrate") was filed by Bank Of America Na on May 26, 2022.
What is this patent about?
’681 is related to the field of semiconductor device fabrication, specifically addressing challenges in preparing wafers for direct bonding after test probing. Test probes leave physical marks and protrusions on probe pads, disrupting the flatness required for successful direct bonding processes like wafer-to-wafer or die-to-wafer bonding. This is particularly relevant in advanced packaging techniques where precise alignment and strong bonding are crucial.
The underlying idea behind ’681 is to mitigate the impact of probe pad damage on direct bonding by either filling and planarizing the damaged areas, recessing the probe pads, or substituting a hybrid bonding layer for a conventional metallization layer. The goal is to restore a flat, uniform surface suitable for direct bonding, even after the probe pads have been physically disrupted during testing. This involves clever manipulation of metal and dielectric layers to create a planarized surface with suitable interconnects.
The claims of ’681 focus on structures and methods for creating a direct bonding surface on a semiconductor substrate after probe pads have been damaged during testing. The independent claims cover structures with buried probe pads, insulating layers, and operational interconnects arranged to facilitate direct hybrid bonding . They also cover methods of depositing insulating layers, patterning openings for interconnects, and planarizing the surface to achieve the required flatness for bonding.
In practice, the invention can be implemented in several ways. One approach involves depositing a metal layer over the damaged probe pads, planarizing it to create a flat surface, and then forming interconnects through a dielectric layer. Another approach involves recessing the probe pads into lower metallization layers, creating cavities that isolate the damaged areas from the bonding interface. A third approach replaces a conventional metallization layer with a hybrid bonding layer, eliminating the need for additional mask layers. These methods ensure that the protrusions from probe pad damage do not interfere with the direct bonding process.
Unlike conventional solutions that add sacrificial metallization layers, ’681 offers more efficient and cost-effective approaches. By either filling and planarizing, recessing the probe pads, or substituting a metallization layer with a hybrid bonding layer, the invention avoids the need for additional processing steps or materials. The use of liquid metal in recessed cavities for test probing is also a novel approach that prevents damage to the probe pads in the first place. These innovations improve the yield and reliability of direct bonding processes in advanced semiconductor packaging.
How does this patent fit in bigger picture?
Technical landscape at the time
In the late 2010s when ’681 was filed, semiconductor manufacturing processes were at a stage when direct bonding techniques were becoming increasingly important for advanced packaging. At a time when wafer-to-wafer and die-to-wafer bonding were typically implemented using oxide-oxide direct bonding or hybrid bonding, the planarity of the surfaces to be bonded was critical. When hardware or software constraints made it non-trivial to avoid probe pad damage during testing, alternative solutions were needed to ensure high bonding yields.
Novelty and Inventive Step
The examiner allowed the claims because the amended independent claims require operational interconnects on opposite lateral sides of the probe pad on a bonding surface, where both sides of the substrate are prepared for direct bonding using operational interconnects. The prior art only shows these interconnects on one lateral side of a probe pad or dummy interconnects on both lateral sides. The examiner considered that these amendments, in combination with the remaining claim limitations, made the claims allowable over the prior art.
Claims
There are 31 claims in total. Independent claims are claims 1, 11, 21, and 27. The independent claims generally focus on a structure, a bonded structure, a semiconductor device, and a method for direct hybrid bonding, respectively, all involving a buried probe pad. The dependent claims generally elaborate on the features and configurations described in the independent claims.
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Date
Description
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US11978681
- Application Number
- US17825240
- Filing Date
- May 26, 2022
- Status
- Granted
- Expiry Date
- Apr 10, 2040
- External Links
- Slate, USPTO, Google Patents