Package-on-Package Warpage Control via Microwave Heating
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Solution Overview
Problem
High-temperature processing steps in the fabrication of 3D integrated chips lead to mechanical stress, causing warpage, cracking, delamination, and void formation in package-on-package semiconductor structures due to differences in thermal expansion properties between substrates and electrically-insulating adhesives.
Innovation Solution
A tool arrangement combining a variable frequency microwave source and a pressure generator is used to heat and apply elevated pressure to the package-on-package semiconductor structure, limiting warpage and preventing void formation within the electrically-insulating adhesive by evenly distributing energy and isolating the structure from ambient environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature processing steps are used to cure the electrically-insulating adhesive, then the adhesive bonding strength is improved, but warpage and mechanical stress increase
Solution Approach 1:
The patent applies microwave radiation to heat the adhesive layer uniformly, changing the heating parameter from conventional convection to electromagnetic radiation. This allows achieving adequate bonding strength while minimizing thermal gradients that cause warpage
Solution Approach 2:
The patent replaces conventional convection heating with microwave heating, substituting a mechanical thermal field with an electromagnetic field that can penetrate and heat the adhesive layer more uniformly, reducing mechanical stress and warpage
2Strength
If high-temperature processing steps are used to cure the electrically-insulating adhesive, then the adhesive bonding strength is improved, but cracking and delamination occur
Solution Approach 1:
The patent uses microwave radiation to achieve uniform heating of the adhesive layer, changing the thermal parameter distribution from gradient-based (convection) to uniform (electromagnetic penetration). This reduces thermal shock that causes cracking and delamination while maintaining bonding strength
Solution Approach 2:
The patent substitutes conventional convection heating with microwave heating, replacing a mechanical thermal field that creates surface heating and thermal gradients with an electromagnetic field that provides volumetric heating, thereby preventing cracking and delamination
3Ease of manufacture
If conventional convection heating methods are used, then the process is simple, but warpage and void formation occur
Solution Approach 1:
The patent replaces conventional convection heating with microwave heating, substituting a simple but ineffective mechanical thermal field with an electromagnetic field that provides uniform energy distribution, eliminating warpage while maintaining processability
Solution Approach 2:
The patent changes the heating parameter from convection-based surface heating to microwave-based volumetric heating, achieving uniform temperature distribution that prevents warpage and void formation while curing the adhesive
4Adaptability or versatility
If different thermal expansion properties of substrates and adhesives are considered, then material selection is optimized, but thermal stress during processing increases
Solution Approach 1:
The patent replaces convection heating with microwave heating, substituting a mechanical thermal field that exacerbates thermal expansion differences with an electromagnetic field that heats materials based on their dielectric properties, thereby reducing thermal stress despite material compatibility constraints
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 significantly reduces warpage and eliminates voids in the adhesive, improving the structural integrity and electrical properties of the semiconductor package, compared to conventional convection heating methods.
Implementation Method 1
A tool arrangement combining a variable frequency microwave source and a pressure generator is used to heat and apply elevated pressure to the package-on-package semiconductor structure
Implementation Method 2
heating by the variable frequency microwave source... evenly distributing energy
Implementation Method 3
apply elevated pressure to the package-on-package semiconductor structure, limiting warpage and preventing void formation
Data Source
AI summary
The present disclosure relates to a tool arrangement and method to reduce warpage within a package-on-package semiconductor structure, while minimizing void formation within an electrically-insulating adhesive which couples the packages. A pressure generator and a variable frequency microwave source are coupled to a process chamber which encapsulates a package-on-package semiconductor structure. The package-on-package semiconductor structure is simultaneously heated by the variable frequency microwave source at variable frequency, variable temperature, and variable duration and exposed to an elevated pressure by the pressure generator. This combination for microwave heating and elevated pressure limits the amount of warpage introduced while preventing void formation within an electrically-insulating adhesive which couples the substrates of the package-on-package semiconductor structure.