Direct-Bonding Surface Preparation to Preserve Sharp Cavity Edges
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Solution Overview
Problem
In microelectronics fabrication, the CMP process often leads to undesirable rounding of cavity edges in oxide surfaces, which can degrade the quality of direct bonds and increase the bonding seam dimensions.
Innovation Solution
A temporary filler with similar chemical and mechanical properties to the oxide surface is used to overfill cavities and trenches, allowing CMP to planarize the filler down to the oxide surface without rounding the edges. The temporary filler is then selectively removed using an etchant that does not react with the oxide surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP process is applied to planarize the oxide surface, then surface flatness is improved, but cavity edge rounding occurs
Solution Approach 1:
The patent applies preliminary action by depositing a sacrificial filler material into the cavities before the CMP process. This filler material has similar polishing characteristics to the oxide, so it protects the cavity edges from rounding during planarization. The filler is then selectively removed after CMP, leaving sharp cavity edges on the now-planarized surface.
Solution Approach 2:
The sacrificial filler material acts as an intermediary that temporarily occupies the cavities during CMP. This intermediary material has been specifically selected to have polishing properties matching the oxide, allowing it to serve as a protective placeholder that prevents edge rounding while enabling surface planarization.
2Manufacturing precision
If photoresist is stripped from the oxide surface, then cleanliness is improved, but surface roughening occurs
Solution Approach 1:
The patent replaces the mechanical/chemical photoresist stripping process with a deposition- CMP-etch sequence. Instead of using plasma or chemical strippers that roughen the surface, the method uses CMP (a mechanical polishing process) on the sacrificial filler that has matching polishing characteristics, thereby achieving cleaning without surface roughening.
3Device complexity
If cavity edges are left open during CMP, then process simplicity is improved, but dielectric erosion occurs
Solution Approach 1:
The patent applies preliminary action by pre-filling the cavities with sacrificial material before CMP. This preliminary step prevents dielectric erosion during the polishing process, as the filler material protects the cavity edges from excessive material removal while maintaining process simplicity.
Solution Approach 2:
The patent changes the physical state and composition parameters of the cavity contents by introducing a sacrificial filler material with specific polishing characteristics. This parameter change enables the cavity edges to maintain their shape during CMP, preventing dielectric erosion while keeping the overall process relatively simple.
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 method ensures sharp corners at the edges of cavities, minimizing bond seams and enhancing the integrity and quality of direct bonds in microelectronics.
Implementation Method 1
The temporary filler is then removed with an etchant that is selective to the temporary filler, but nonreactive toward the oxide surface and toward inner surfaces of the cavities and trenches in the oxide bonding surface.
Implementation Method 2
The CMP process is applied to the temporary filler to flatten the temporary filler down to the oxide bonding surface.
Data Source
AI summary
Improved bonding surfaces for microelectronics are provided. An example method of protecting a dielectric surface for direct bonding during a microelectronics fabrication process includes overfilling cavities and trenches in the dielectric surface with a temporary filler that has an approximately equal chemical and mechanical resistance to a chemical-mechanical planarization (CMP) process as the dielectric bonding surface. The CMP process is applied to the temporary filler to flatten the temporary filler down to the dielectric bonding surface. The temporary filler is then removed with an etchant that is selective to the temporary filler, but nonreactive toward the dielectric surface and toward inner surfaces of the cavities and trenches in the dielectric bonding surface. Edges of the cavities remain sharp, which minimizes oxide artifacts, strengthens the direct bond, and reduces the bonding seam.