Wafer-to-Wafer Bonding with Polymer Layer
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Solution Overview
Problem
Conventional wafer-to-wafer bonding methods using copper pads and dummy patterns often result in bonding defects due to gaps and voids, leading to unreliable bonding forces.
Innovation Solution
A wafer-to-wafer bonding structure that employs copper pads with barrier metal layers and polymer layers, where the polymer layers cover the edges and bevel areas, allowing for direct bonding without dummy patterns, using materials like polyimide, polyamide, or polyacrylate that harden and provide a strong bonding force through thermal treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If dummy patterns are used to bond wafers, then bonding force is secured, but bonding defects occur due to gaps and voids in the dummy pattern
Solution Approach 1:
The patent removes the dummy pattern from the bonding structure entirely. Instead of using dummy Cu pads, the invention uses only the functional Cu pads that are necessary for device operation, thereby eliminating the source of bonding defects while maintaining adequate bonding force through optimized functional pad design and polymer layer support.
Solution Approach 2:
The patent introduces a polymer layer as an intermediary material between the Cu pads and the bonding interface. This polymer layer fills the spaces between pads, provides uniform bonding force distribution, and prevents gap formation, thereby eliminating bonding defects without requiring dummy patterns.
2Strength
If dummy patterns are formed to maintain bonding force, then bonding strength is improved, but device complexity increases due to additional patterns
Solution Approach 1:
The patent eliminates the dummy pattern component entirely from the bonding structure, retaining only the functional Cu pads required for device operation. This extraction of unnecessary elements reduces pattern complexity while maintaining bonding strength through alternative mechanisms.
Solution Approach 2:
The functional Cu pads serve dual purposes: they provide electrical connectivity for device operation and simultaneously serve as bonding elements. The polymer layer also serves multiple functions by filling gaps, providing bonding force distribution, and preventing void formation, thereby eliminating the need for separate dummy patterns.
3Ease of manufacture
If Cu pads are bonded directly without polymer layer, then manufacturing is simpler, but gaps and voids are generated in bonded portion
Solution Approach 1:
The patent introduces a polymer layer as an intermediary material between the Cu pads during bonding. This polymer layer flows into and fills gaps between pads, preventing void formation and ensuring high-quality bonded portions. The polymer layer is applied through standard coating processes, maintaining manufacturing simplicity while dramatically improving bonded portion quality.
Solution Approach 2:
The patent changes the physical state and properties of the polymer layer during the bonding process. The polymer is applied in a soft, moldable state that allows it to fill gaps and conform to surface variations, then it is cured to provide structural support. This parameter change enables the polymer to simultaneously improve manufacturing precision and maintain process simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces or eliminates defects caused by gaps and voids, maintaining a strong bonding force between wafers without the need for dummy patterns, ensuring reliable wafer bonding.
Implementation Method 1
using materials like polyimide, polyamide, or polyacrylate that harden and provide a strong bonding force through thermal treatment
Implementation Method 2
A wafer-to-wafer bonding structure that employs copper pads with barrier metal layers and polymer layers, where the polymer layers cover the edges and bevel areas, allowing for direct bonding without dummy patterns
Data Source
AI summary
A wafer-to-wafer bonding structure may include: a first wafer including a first insulating layer on a first substrate and on a first copper (Cu) pad that penetrates the first insulating layer and has portions protruding from an upper surface of the first insulating layer, and a first barrier metal layer on a lower surface and sides of the first Cu pad; a second wafer including a second insulating layer on a second substrate and on a second copper (Cu) pad that penetrates the second insulating layer, has portions protruding from an upper surface of the second insulating layer, and is bonded to the first Cu pad, and a second barrier metal layer on a lower surface and sides of the second Cu pad; and a polymer layer covering protruding sides of the first and second barrier metal layers and disposed between the first and second wafers.