Semiconductor Die Singulation via Laser-Induced Crack Propagation
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Solution Overview
Problem
Current methods for singulating semiconductor die from wafers are inefficient, leading to high manufacturing time, uncontrollable crack propagation, incompatibility with backmetal layers, and limitations on die size reduction, with existing techniques like scribing and thermal laser separation being slow and damaging.
Innovation Solution
The method involves forming trenches within scribe lines on the wafer, locally heating these trenches using a thermal laser to create stress, and then cooling to initiate controlled crack propagation, which helps in singulating the die with improved precision and compatibility with backmetal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If scribing or dicing is used to cut through the wafer, then the die can be separated from the wafer, but the scribe grid width is large (about 150 microns) which consumes a large portion of the semiconductor wafer and reduces the number of die per wafer
Solution Approach 1:
The patent replaces the mechanical dicing wheel cutting system with a laser-based system that uses light energy to induce thermal stress and crack propagation. This substitution allows for much narrower scribe lines since the laser can be focused to a small spot size, thereby reducing the area consumed per scribe line and increasing the number of die per wafer while maintaining effective separation.
Solution Approach 2:
The patent changes the fundamental parameter of scribe line width by transitioning from mechanical cutting (requiring wide paths for the dicing wheel) to laser-induced cracking (which can occur along very narrow lines). This parameter change enables significantly reduced scribe line widths, optimizing wafer utilization.
2Manufacturing precision
If scribing is performed on the entire semiconductor wafer, then all die can be separated, but the time required is over one hour or more which reduces the throughput and manufacturing capacity
Solution Approach 1:
The patent replaces the slow mechanical scribing process with a laser-based system that induces rapid crack propagation. The laser method eliminates the need for gradual mechanical cutting, enabling much faster singulation times while achieving complete separation of all die from the wafer, thereby significantly improving throughput and manufacturing capacity.
Solution Approach 2:
The patent employs periodic or pulsed laser action to induce crack propagation along scribe lines. By using controlled laser pulses rather than continuous mechanical cutting, the system achieves rapid singulation across the entire wafer in a fraction of the time required by traditional scribing methods.
3Productivity
If thermal laser separation is used, then the singulation time is reduced, but the crack propagation is uncontrollable and it is not compatible with backmetal layers
Solution Approach 1:
The patent applies local quality by creating trenches or grooves at specific locations along the scribe lines before applying the laser. These pre-formed features concentrate the thermal stress and guide crack propagation along the desired path, providing controllable and reliable singulation that is compatible with backmetal layers, while maintaining the speed advantages of laser-based methods.
Solution Approach 2:
The patent introduces trenches as an intermediary structure that mediates between the laser energy and the wafer material. These trenches act as stress concentrators that guide and control crack propagation, ensuring reliable and controllable singulation while maintaining compatibility with backmetal layers and achieving fast processing speeds.
4Device complexity
If traditional methods are used, then the process is simple, but the die size reduction is limited and device electrical characteristics are degraded
Solution Approach 1:
The patent replaces mechanical cutting methods with laser-induced crack propagation, enabling much narrower scribe lines that allow for significant die size reduction. This substitution maintains process simplicity while removing the limitations on miniaturization that constrain traditional mechanical methods, thereby enabling smaller die sizes without degrading device electrical characteristics.
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 singulation time, allows for smaller die sizes, and provides more uniform and reliable separation with narrower scribe lines, enhancing manufacturing efficiency and device reliability while being compatible with backside coatings and backmetal layers.
Implementation Method 1
heating the trenches with a thermal laser to form a localized stress in the trenches
Implementation Method 2
cooling the trenches thereby propagating cracks within the trenches
Implementation Method 3
forming localized stresses within the trenches to form cracks within the trenches and propagating the cracks through the semiconductor wafer
Data Source
AI summary
In one embodiment, semiconductor die are singulated from a semiconductor wafer by forming trenches along singulation lines and initiating a cracks from within the trenches, which propagate through the semiconductor wafer in a more controlled manner.