Probe Pad Recess and Planarization for Direct Bonding Surfaces
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Solution Overview
Problem
Conventional methods for mitigating probe pad damage during test probing, such as adding sacrificial metallization layers or sacrificial probe pads, are cumbersome and expensive, and result in surface disruptions that hinder direct bonding processes like wafer-to-wafer or die-to-wafer bonding.
Innovation Solution
Methods and layer structures that include depositing and planarizing metal over probe pads, recessing probe pads into cavities, or embedding them in dielectric materials, and using liquid metals for electrical connections, to restore a flat surface suitable for direct bonding without increasing the number of metallization mask layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test probes make physical contact with probe pads, then electrical connections for testing are established, but probe marks and surface protrusions are created that disrupt the flatness of the substrate surface
Solution Approach 1:
The patent applies preliminary action by forming recesses in the substrate surface before probe pad formation, or by providing sacrificial probe pads that are removed before direct bonding. This pre-prepared structure ensures that when probes contact the pads, any surface disruption occurs within the recess or sacrificial layer, preserving the overall surface flatness for subsequent bonding operations.
Solution Approach 2:
The patent uses an intermediary approach by introducing sacrificial probe pads made of different material properties, or by using recess structures as intermediate zones. These intermediaries absorb the mechanical stress and surface disruption from probe contact, protecting the main substrate surface from damage while still allowing electrical testing to proceed.
2Manufacturing precision
If sacrificial metallization layers or sacrificial probe pads are added to mitigate probe pad damage, then probe pad surface disruption is reduced, but the fabrication process complexity and cost increase
Solution Approach 1:
The patent applies the extraction principle by removing sacrificial probe pads after they have served their protective function during testing, or by eliminating the need for additional sacrificial metallization layers through clever recess design. This extraction approach maintains probe pad surface integrity while avoiding the permanent addition of complex structural elements.
Solution Approach 2:
The patent achieves multi-functionality by designing recess structures that serve multiple purposes: they contain probe-induced surface disruptions, provide mechanical support, and enable both testing and subsequent bonding operations without requiring separate sacrificial layers. This universal design reduces overall fabrication complexity while maintaining probe pad integrity.
3Ease of manufacture
If probe pad protrusions are allowed to exist, then the fabrication process remains simple, but the flatness of the substrate surface is compromised for direct bonding processes
Solution Approach 1:
The patent applies preliminary action by pre-forming recesses in the substrate before probe pad creation, or by strategically placing sacrificial elements that will be removed later. This advance preparation allows the use of simple probe testing procedures while ensuring that the final substrate surface maintains the required flatness for direct bonding, as the disruptions are contained within the pre-designed recess structures.
Data Source
AI summary
Mitigating surface damage of probe pads in preparation for direct bonding of a substrate is provided. Methods and layer structures prepare a semiconductor substrate for direct bonding processes by restoring a flat direct-bonding surface after disruption of probe pad surfaces during test probing. An example method fills a sequence of metals and oxides over the disrupted probe pad surfaces and builds out a dielectric surface and interconnects for hybrid bonding. The interconnects may be connected to the probe pads, and/or to other electrical contacts of the substrate. A layer structure is described for increasing the yield and reliability of the resulting direct bonding process. Another example process builds the probe pads on a next-to-last metallization layer and then applies a direct bonding dielectric layer and damascene process without increasing the count of mask layers. Another example process and related layer structure recesses the probe pads to a lower metallization layer and allows recess cavities over the probe pads.