Wafer Dicing via Laser Plasma Etch and Backside Grind
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Solution Overview
Problem
Current methods for dicing semiconductor wafers, such as scribing and sawing, often result in chipping, cracking, and waste of wafer real estate, while plasma dicing faces cost and implementation limitations, particularly with metals like copper.
Innovation Solution
A hybrid method combining laser scribing to form a patterned mask, plasma etching to create trenches, and backside grinding to singulate dies, which reduces chipping and cracking and increases throughput by using a femtosecond laser for precise ablation and an ultra-high-density plasma source for efficient etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scribing or sawing is used for wafer dicing, then the wafer can be separated into individual dies, but chips and gouges form along the severed edges and cracks propagate into the substrate
Solution Approach 1:
The patent replaces mechanical scribing and sawing systems with a laser-based system that uses optical energy to ablate material and create separation trenches. The laser beam melts and vaporizes material through controlled heating, eliminating mechanical contact that causes chipping and cracking while achieving clean die edges.
Solution Approach 2:
The patent controls laser parameters (power, pulse duration, scanning speed) to precisely control the ablation process. By adjusting these parameters, the laser can selectively remove material along street regions without excessive heat diffusion that would cause cracking, thereby improving die edge quality while maintaining dicing capability.
2Reliability
If additional spacing is required between dies to prevent damage, then chipping and cracking are reduced, but wafer real estate is wasted and fewer dies can be formed
Solution Approach 1:
The laser-based dicing system creates narrow separation trenches with precise control, eliminating the need for wide spacing buffers required by mechanical methods. The laser can accurately confine energy to street regions, allowing dies to be placed closer together while still preventing damage during separation.
3Productivity
If a diamond tipped saw is used for thicker wafers, then dicing can be performed, but three to five hundred microns must separate the circuitry and substantial cleaning is required
Solution Approach 1:
The laser system replaces the mechanical saw with optical ablation, creating narrow trenches without the 15-micron blade thickness constraint. This allows circuitry to be placed closer together while still enabling thick wafer dicing, and the laser's precise energy confinement eliminates the need for extensive cleaning operations.
4Productivity
If plasma dicing is implemented, then dicing can be performed, but cost increases and production issues arise with metals like copper
Solution Approach 1:
The patent uses laser ablation instead of plasma processing, replacing a chemical-based method with an optical one. This approach is more cost-effective and avoids plasma-related production issues with copper and other metals, as the laser can selectively ablate materials based on their optical absorption properties without causing plasma-induced contamination or processing challenges.
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 hybrid approach achieves clean and precise die singulation with reduced waste, improved throughput, and effective handling of challenging materials like copper, enhancing the dicing process for thicker wafers.
Implementation Method 1
A laser beam is directed onto a wafer to melt and vaporize material along street regions between a plurality of integrated circuits formed on the wafer
Implementation Method 2
A plasma source is utilized to plasma etch the wafer to advance the trench partially through the wafer
Implementation Method 3
The wafer is back side ground to reach the etched trench
Data Source
AI summary
Front side laser scribing and plasma etch are performed followed by back side grind to singulate integrated circuit chips (ICs). A mask is formed covering ICs formed on the wafer, as well as any bumps providing an interface to the ICs. The mask is patterned by laser scribing to provide a patterned mask with gaps. The patterning exposes regions of the semiconductor wafer, below thin film layers from which the ICs are formed. The semiconductor wafer is then etched through the gaps in the patterned mask to advance a front of an etched trench partially through the semiconductor wafer thickness. The front side mask is removed, a backside grind tape applied to the front side, and a back side grind performed to reach the etched trench, thereby singulating the ICs.