Heterogeneous Bonding Structure for Coplanar Wafer Bond Pads
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Solution Overview
Problem
The challenge in wafer-to-wafer bonding is achieving co-planarity of bonding surfaces, particularly due to dishing issues during Chemical Mechanical Polish (CMP) processes, which lead to non-planar and rough surfaces on metal pads, hindering effective metal-to-metal bonding.
Innovation Solution
A selective deposition of fill-in conductive layers, such as metal layers, is applied on the recessed metal pads to fill in the non-planarities, followed by a controlled planarization process to ensure the top surfaces of the metal pads and dielectric layers are coplanar, facilitating improved bonding through hybrid bonding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP process is used to planarize wafer surfaces, then surface flatness is improved, but dishing occurs causing non-planar metal pad surfaces
Solution Approach 1:
The patent applies selective fill-in deposition only to recessed metal pad areas rather than uniform planarization across the entire wafer surface. This local quality approach allows the metal pads to be filled to the appropriate level while leaving the surrounding dielectric surface undisturbed, thereby achieving coplanarity without the dishing problems associated with global CMP processing.
2Manufacturing precision
If selective fill-in deposition is applied to metal pads, then coplanarity is improved, but process complexity increases
Solution Approach 1:
The patent performs preliminary selective fill-in deposition of conductive material into recessed metal pad areas before the final bonding process. This preliminary action prepares the surfaces in advance to achieve the required coplanarity, eliminating the need for complex post-processing or advanced CMP techniques while simplifying the overall manufacturing flow.
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 enhances the quality and reliability of wafer-to-wafer bonding by reducing non-coplanarity and roughness, allowing for stable metal-to-metal and oxide-to-oxide bonding with lower bonding pressures and temperatures, thus improving the integrity of the resulting package components.
Implementation Method 1
A selective deposition of fill-in conductive layers, such as metal layers, is applied on the recessed metal pads to fill in the non-planarities
Implementation Method 2
followed by a controlled planarization process to ensure the top surfaces of the metal pads and dielectric layers are coplanar
Implementation Method 3
In the hybrid bonding, the metal pads of two wafers are bonded to each other through direct metal-to-metal bonding, and an oxide surface of one of the two wafers is bonded to an oxide surface or a silicon surface of the other wafer
Data Source
AI summary
A method includes forming a first package component, which formation process includes forming a first plurality of openings in a first dielectric layer, depositing a first metallic material into the first plurality of openings, performing a planarization process on the first metallic material and the first dielectric layer to form a plurality of metal pads in the first dielectric layer, and selectively depositing a second metallic material on the plurality of metal pads to form a plurality of bond pads. The first plurality of bond pads comprise the plurality of metal pads and corresponding parts of the second metallic material. The first package component is bonded to a second package component.