Wafer-Level Underfill Laser Stealth Dicing
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Solution Overview
Problem
Current methods for dicing semiconductor wafers, such as scribing and sawing, result in chipping, cracking, and waste of wafer real estate due to jagged separation lines and the need for significant spacing between dice, while plasma dicing faces cost and implementation limitations.
Innovation Solution
A stealth dicing method involving laser irradiation from the backside of the wafer to generate defects along dicing streets, followed by mechanical singulation, which allows for clean separation and reduced waste by using a wafer-level underfill material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scribing or sawing is used to dice wafers, then the wafer can be separated into individual dice, but chipping and cracking occur along the severed edges and additional spacing must be added between dice
Solution Approach 1:
The patent replaces traditional mechanical dicing methods (scribing with diamond tips or sawing with rotating blades) with a laser-based system. The laser irradiates the wafer from the backside to generate defects along the dicing streets, which then guide crack propagation to achieve clean separation without mechanical contact. This substitution eliminates the chipping and cracking caused by mechanical forces while allowing dice to be placed closer together, improving wafer real estate utilization.
2Productivity
If sawing is used with a thick blade, then the wafer can be cut through, but three to five hundred microns must separate the circuitry to prevent damage
Solution Approach 1:
The patent replaces the mechanical sawing process with laser irradiation that generates defects and guides crack propagation without physical contact. This eliminates the need for large spacing (three to five hundred microns) required when using thick saw blades, as the laser method does not mechanically stress the wafer or generate particulate contamination that could damage the integrated circuits.
Solution Approach 2:
The patent introduces laser-generated defects as an intermediary mechanism between the laser energy and the final crack propagation. These defects act as stress concentrators that guide the crack along the desired dicing street path, enabling precise separation without the need for large safety margins around the circuitry.
3Manufacturing precision
If scribing is used, then thin wafers can be separated, but only one side of the die can be scribed in the direction of the crystalline structure resulting in jagged separation lines
Solution Approach 1:
The patent inverts the traditional scribing approach by irradiating the wafer from the backside rather than the front side. This allows the laser to generate defects and guide crack propagation through the entire wafer thickness without being constrained by the crystalline structure orientation on the front surface, resulting in clean separation lines on both sides of each die.
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 enables precise and clean separation of dice with reduced chipping and cracking, optimizing wafer real estate usage and overcoming the limitations of traditional dicing methods.
Implementation Method 1
laser irradiating the semiconductor wafer from a backside of the semiconductor wafer to generate defects along dicing streets of the semiconductor wafer
Data Source
AI summary
Methods of dicing semiconductor wafers, each wafer having a plurality of integrated circuits, are described. In an example, a method of dicing a wafer involves providing a semiconductor wafer having integrated circuits on a front side thereof, and having a wafer-level underfill material layer disposed on the integrated circuits. The method also involves laser irradiating the semiconductor wafer from a backside of the semiconductor wafer to generate defects along dicing streets of the semiconductor wafer, the dicing streets oriented between the integrated circuits. The method also involves, subsequent to the laser irradiating, mechanically singulating the integrated circuits along the dicing streets.