Probe Pad Surface Restoration for Flat Direct Bonding
Find Innovative SolutionsGenerate Solutions
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, applying dielectric materials, and creating recessed cavities to embed or isolate probe pads, ensuring a flat surface for direct bonding, and using liquid metals for electrical connections without disrupting the solid surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test probing is performed on probe pads, then electrical connections for testing are established, but surface disruptions and protrusions are created that interfere with direct bonding processes
Solution Approach 1:
The probe pad structure is segmented into multiple functional layers: the original probe pad, an embedded recessed cavity structure, and a restoration layer. This segmentation allows the probe pad to serve both testing and bonding functions by separating the electrical connection function (probe pad) from the surface flatness function (restoration layer and recessed cavity).
Solution Approach 2:
The recessed cavity is formed and the probe pad is embedded within it before the direct bonding process. This preliminary action ensures that the probe pad protrusion problem is addressed in advance, allowing the surface to be restored to flatness before bonding occurs, thus preventing interference with the bonding interface.
2Reliability
If sacrificial metallization layers are added to mitigate probe pad damage, then probe pad protection is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The recessed cavity structure serves multiple functions simultaneously: it protects the probe pad from damage during testing, provides a means to restore surface flatness, and does not require additional sacrificial metallization layers. This multi-functionality reduces overall device complexity while maintaining probe pad integrity.
Solution Approach 2:
Instead of adding complex sacrificial structures, the invention uses a simpler recessed cavity approach that replicates the protective function without the added complexity of multiple metallization layers. The recessed cavity effectively 'copies' the protection function in a more efficient manner.
3Ease of operation
If probe pads are left exposed on the surface, then electrical access for testing is maintained, but the protrusions ruin flatness required for direct bonding
Solution Approach 1:
The probe pad is nested within the recessed cavity, allowing the probe pad to be accessible for electrical connections while being contained within a structure that maintains surface flatness. The nesting arrangement enables both probe access and bonding compatibility simultaneously.
Solution Approach 2:
The recessed cavity provides localized protection and containment for the probe pad, applying the flatness restoration solution only where needed (at the probe pad location) rather than requiring global surface modification. This local quality approach maintains ease of probe access while ensuring bonding surface flatness.
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.