Light-Absorbing Wafer Dicing Mask for Clean Laser-Plasma Singulation
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Solution Overview
Problem
Current semiconductor wafer dicing methods, such as scribing and sawing, often result in chipping, cracking, and waste of wafer real estate due to jagged separation lines and damage to integrated circuits, while plasma dicing faces cost and production issues with metal etching.
Innovation Solution
A method using a water-soluble light-absorbing mask with a femtosecond laser for scribing and subsequent plasma etching to singulate semiconductor wafers, minimizing damage and optimizing etch selectivity with a composite mask that includes light-absorber species and particles for improved etch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If scribing is used to separate dice, then the separation process is simple and quick, but chipping and cracking occur along the severed edges
Solution Approach 1:
The patent segments the dicing process into two distinct stages: laser scribing to create initial separation lines, and plasma etching to complete the separation. This segmentation allows each process to optimize for its specific function, with laser providing speed and plasma providing clean separation without mechanical contact
Solution Approach 2:
The patent replaces the mechanical diamond scribe with a laser-based system that uses optical energy to ablate material and create separation lines. This substitution eliminates mechanical contact that causes chipping and cracking, while maintaining the speed advantage of scribing
2Reliability
If sawing is used to separate thicker wafers, then the separation is clean and reliable, but wafer real estate is wasted due to blade thickness and required spacing
Solution Approach 1:
The patent replaces the mechanical saw blade with a laser plasma system that uses optical and plasma energy to etch separation lines. This eliminates the need for physical blade contact, reducing the kerf width from hundreds of microns to micrometer-scale precision, thereby maximizing usable wafer area
Solution Approach 2:
The patent changes the operating parameters by using laser-induced plasma at controlled energy levels to achieve precise etching. The plasma process parameters (power, gas flow, pressure) are optimized to create clean separations with minimal lateral etching, maintaining separation quality while reducing width
3Reliability
If plasma dicing is used to avoid chipping and cracking, then edge integrity is improved, but cost and production throughput are reduced
Solution Approach 1:
The patent segments the dicing process into two stages: a rapid laser scribing stage that creates initial separation lines quickly, followed by a plasma etching stage that completes the separation cleanly. This segmentation allows the system to achieve both high throughput (from laser) and high reliability (from plasma)
Solution Approach 2:
The laser scribing performs preliminary action by creating initial separation lines and removing most material before plasma etching. This preliminary action reduces the workload for the plasma process, allowing it to operate at higher power levels for longer durations without compromising throughput, thereby improving edge integrity
4Reliability
If wider spacing is provided between dice to prevent damage, then chip and crack formation is reduced, but wafer real estate is wasted
Solution Approach 1:
The patent replaces mechanical separation methods with laser-induced plasma etching that operates with micrometer-scale precision. This precision eliminates the need for conservative spacing margins, allowing dice to be placed closer together while maintaining circuit safety from damage
Solution Approach 2:
The patent changes the separation process parameters to achieve cleaner, more precise cuts with minimal lateral damage zones. By optimizing plasma power, gas composition, and exposure time, the process creates narrow separation lines that maximize usable wafer area while protecting circuits
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 laser damage zones, minimizes chipping and delamination, and enhances etch selectivity, allowing for more efficient and precise dicing with reduced waste and improved integration circuit integrity.
Implementation Method 1
The mask is patterned with a laser scribing process to provide a patterned mask with gaps
Implementation Method 2
The substrate is then plasma etched through the gaps in the patterned mask to singulate the integrated circuits
Implementation Method 3
a mask is formed which includes a water soluble mask material and a light absorber
Data Source
Figure 1
Figure 2A~2C
Figure 3A
AI summary
Light-absorbing masks and methods of dicing semiconductor wafers are described. In an example, a method of dicing a semiconductor wafer including a plurality of integrated circuits involves forming a mask above the semiconductor wafer. The mask includes a water-soluble matrix based on a solid component and water, and a light-absorber species throughout the water- soluble matrix. The mask and a portion of the semiconductor wafer are patterned with a laser scribing process to provide a patterned mask with gaps and corresponding trenches in the semiconductor wafer in regions between the integrated circuits. The semiconductor wafer is plasma etched through the gaps in the patterned mask to extend the trenches and to singulate the integrated circuits. The patterned mask protects the integrated circuits during the plasma etching.