Wafer Scribe Trench Ablation for Low-Damage Die Separation
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Solution Overview
Problem
Laser cutting in die singulation leads to uncontrolled crack propagation and laser splash, causing damage to active circuitry and reducing product yield, with damage often undetected until final device testing post-packaging.
Innovation Solution
A method involving laser ablation to form trenches in a scribe region between die regions, followed by wafer probe testing to identify damage, and subsequent wafer expansion to separate individual semiconductor dies, mitigating laser splash and enabling early detection of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser cutting is used to separate semiconductor dies from a wafer, then die singulation can be achieved, but uncontrolled crack propagation and laser splash occur causing damage to active circuitry
Solution Approach 1:
The patent applies preliminary action by performing laser ablation to create a trench in the scribe region before the wafer expansion process. This pre-formed trench provides a controlled path for crack propagation during subsequent die separation, preventing uncontrolled crack spread across the wafer and reducing laser splash damage to active circuitry.
Solution Approach 2:
The patent segments the laser processing into two distinct stages: first creating a trench in the scribe region, then performing wafer expansion to separate dies. This segmentation allows the laser energy to be concentrated in the non-active scribe area first, isolating the harmful effects from the active circuit regions while still achieving effective die separation.
2Productivity
If laser cutting is used to separate dies, then die separation can be achieved, but crack propagation breaches the device scribe seal causing meander faults
Solution Approach 1:
The trench is created in advance in the scribe region before die separation. This preliminary structure guides the crack propagation path during wafer expansion, ensuring cracks follow the pre-defined trench rather than breaching the scribe seal, thereby maintaining manufacturing precision and scribe seal integrity.
Solution Approach 2:
The trench acts as an intermediary structure between the laser processing and the die separation processes. It serves as a controlled interface that manages crack propagation, preventing direct interaction between the expansion forces and the scribe seal, thus protecting seal integrity while enabling effective die separation.
3Productivity
If laser ablation is performed deeply through the wafer, then complete die separation can be achieved, but damage to active circuit portion increases
Solution Approach 1:
The laser ablation is segmented to affect only the scribe region between dies rather than the entire wafer thickness uniformly. By concentrating the ablation in the non-active scribe areas, complete die separation is achieved without exposing the active circuit portions to harmful laser energy, thus reducing active circuit damage.
Solution Approach 2:
The laser ablation process applies local quality by selectively removing material only in the scribe regions where no active circuits exist. This localized processing achieves complete die separation while preserving the integrity of active circuit portions, as the harmful laser effects are confined to areas without sensitive electronics.
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
Facilitates early identification of laser splash damage, improving product yield and reducing manufacturing costs by avoiding packaging of damaged dies.
Implementation Method 1
performing a laser ablation process that removes a portion of a wafer to form a trench in a scribe region between adjacent die regions of the wafer
Data Source
AI summary
A method includes performing a laser ablation process that removes a portion of a wafer to form a trench in a scribe region between adjacent die regions of the wafer, the trench extending from a first side of the wafer toward an opposite second side of the wafer, the trench extending through a metallization structure and an active circuit portion of the wafer, and a bottom of the trench spaced apart from the second side of the wafer. The method also includes performing a wafer expansion process that separates individual semiconductor dies from the wafer after the laser ablation process.