Backside Metal Patterning for Thin-Substrate Die Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current die singulation methods face challenges in efficiently separating semiconductor die from thinned substrates without causing damage, particularly when handling thin substrates, as they often require flipping the substrate and can result in roughened sidewalls and increased handling risks.
Innovation Solution
The method involves forming a backside metal layer and a seed layer on the substrate, applying a photoresist layer, patterning, and using either plasma etching or a laser/saw blade to singulate the die, with remote plasma healing to smooth sidewalls and reduce metal re-deposition, allowing for die separation from the backside without flipping the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional die singulation methods are used on thinned substrates, then die separation can be achieved, but substrate handling complexity increases and damage risk increases due to required flipping operations
Solution Approach 1:
The patent inverts the conventional singulation approach by performing etching and singulation from the backside of the substrate rather than the front side. This allows the substrate to be processed without flipping, reducing handling complexity and damage risk to thinned substrates while maintaining effective die separation
2Productivity
If conventional singulation methods are used on thinned substrates, then die separation can be achieved, but sidewall roughness increases leading to higher damage risk
Solution Approach 1:
By performing singulation from the backside, the process avoids creating rough sidewalls on the front surface that would compromise die integrity. The inverted approach allows clean separation without the mechanical stress and surface damage associated with conventional front-side methods
Solution Approach 2:
The patent replaces mechanical sawing or laser cutting with plasma etching to achieve die separation. This substitution eliminates mechanical contact that causes sidewall roughness and potential die damage, producing cleaner separation with smoother sidewalls
3Productivity
If substrate is thinned to less than 50 micrometers for advanced packaging, then packaging density improves, but substrate strength decreases increasing handling risk
Solution Approach 1:
Processing from the backside allows thinned substrates to be handled and processed in a more stable orientation, reducing the risk of breakage. The substrate maintains its structural integrity better when supported from the back during critical processing steps
Solution Approach 2:
The backside metal layer is formed and patterned before final singulation, providing structural reinforcement to the thinned substrate during subsequent processing steps. This preliminary structuring prevents damage to the fragile thinned substrate
4Productivity
If backside metal layer is etched through to singulate die, then die separation is achieved, but metal re-deposition on sidewalls occurs causing contamination
Solution Approach 1:
The patent uses plasma etching with controlled chemistry to remove the backside metal layer without causing re-deposition. The plasma process allows precise removal of metal while maintaining clean sidewalls, eliminating the contamination issue associated with other etching methods
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 die yield by minimizing substrate handling, reducing damage to thin substrates, and achieving smoother sidewalls, while enabling more precise and efficient die separation with reduced risk of metal re-deposition.
Implementation Method 1
Patterning the photoresist layer may include exposing the photoresist layer and developing the photoresist layer
Implementation Method 2
Removing substrate material in the die street and removing seed layer material in the die street may include plasma etching
Implementation Method 3
The method may include remote plasma healing a plurality of sidewalls of the plurality of die after singulating the die
Implementation Method 4
Removing substrate material in the die street may include using either a laser beam or a saw blade
Data Source
AI summary
Implementations of methods of singulating a plurality of die included in a substrate may include forming a plurality of die on a first side of a substrate, forming a backside metal layer on a second side of a substrate, applying a photoresist layer over the backside metal layer, patterning the photoresist layer along a die street of the substrate, and etching through the backside metal layer located in the die street of the substrate. The substrate may be exposed through the etch. The method may also include singulating the plurality of die included in the substrate through removing a substrate material in the die street.