Wafer Wet Singulation via Backside Dicing Trenches
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Solution Overview
Problem
Conventional dicing methods for semiconductor wafers, especially in 3-D chip stacking applications, face challenges with mechanical fragility and reliability issues due to saw-induced crack propagation, requiring large kerf widths and metal crackstop structures, which can lead to chip edge damage and increased costs.
Innovation Solution
A method involving the creation of dicing trenches on the backside of wafers, filled with materials like tungsten or polysilicon, which are then used to separate chips without mechanical cutting, allowing for smaller chip sizes and reduced damage through a wet etch process or gentle force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mechanical saw with blade width of 50 μm is used for dicing, then chip separation can be achieved, but chip edge damage and saw-induced crack propagation occur
Solution Approach 1:
The patent replaces the mechanical saw cutting system with a chemical etching system. Dicing trenches are formed by removing material from the backside of the wafer using chemical etchants that selectively etch through the substrate along predetermined paths, eliminating mechanical contact and associated crack propagation while achieving clean chip separation edges
Solution Approach 2:
The patent introduces dicing trenches as an intermediary structure formed on the backside of the wafer. These trenches serve as predetermined separation paths that guide the singulation process, allowing chips to be separated along controlled trajectories without direct mechanical cutting through the chip edges, thus preventing crack propagation
2Reliability
If metal crackstop structures are added to prevent crack propagation, then chip reliability improves, but fabrication complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for metal crackstop structures by implementing dicing trenches on the backside of the wafer. The trenches provide inherent crack propagation barriers through their geometric configuration and material removal, removing the requirement for additional metal layers while maintaining or improving reliability
Solution Approach 2:
The patent moves the crackstop function from the front side (planar dimension) to the backside (third dimension) of the wafer. By forming dicing trenches through thickness removal on the backside, the solution provides crack propagation resistance in a different spatial dimension, eliminating the need for front-side metal crackstop structures
3Productivity
If larger kerf width is allocated to accommodate mechanical saw and crackstop structures, then chip separation is achieved, but chip size reduces and chip density decreases
Solution Approach 1:
The patent segments the wafer thickness by forming dicing trenches that extend through the substrate from the backside. This segmentation creates discrete separation zones that define chip boundaries without requiring large lateral kerf widths, allowing tighter chip spacing and higher density while maintaining effective separation
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 chip damage, lowers fabrication and scrap costs, and eliminates the need for metal crackstop structures, enabling more precise and efficient singulation with smaller kerf footprints and increased chip density.
Implementation Method 1
The filler material removed from the dicing trenches may be performed by a wet etch process
Data Source
AI summary
A method includes receiving at least one wafer having a front side and a backside, where the front side has a plurality of integrated circuit chips thereon. The backside of the wafer is thinned, a pattern of material is removed from the backside of the wafer to form a plurality of dicing trenches. Each of the dicing trenches are positioned opposite a location on the front side of the wafer that corresponds to edges of each of the plurality of chips. The dicing trenches are filled with a filler material and a dicing support is attached to a front side of the wafer. The filler material is removed from the dicing trenches, and a force is applied to the dicing support to separate each of the plurality of chips on the wafer from each other along the dicing trenches.