Bonded Wafer Laser Dicing With Vertical Ablation Alignment
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Solution Overview
Problem
Conventional laser dicing methods for bonded structures are inefficient, causing thermal damage, debris, and uneven stress, leading to reduced production yield and increased fabrication costs, especially when dicing multiple wafers simultaneously.
Innovation Solution
A system and method for laser dicing bonded structures that form ablation structures within the wafers aligned vertically, using a pulsed laser beam with adjustable focal planes and depth of focus to minimize damage and debris, allowing simultaneous dicing of multiple wafers without the need for cooling water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional laser dicing methods are used on bonded structures, then dicing can be performed, but thermal damage and debris are generated reducing production yield
Solution Approach 1:
The patent employs ultra-short pulsed laser irradiation instead of continuous laser exposure. The laser operates in periodic pulse mode with durations in the range of femtoseconds to picoseconds, allowing the material to cool between pulses and preventing thermal accumulation that causes damage and debris
Solution Approach 2:
The patent replaces conventional mechanical dicing saws with laser ablation technology. This substitution eliminates mechanical contact forces that cause stress concentration and physical damage to the bonded structure, while the laser directly ablates material through photothermal and photomechanical effects without generating mechanical debris
2Reliability
If conventional laser dicing is used, then dicing can be performed, but uneven stress is caused leading to reduced production yield
Solution Approach 1:
The ultra-short pulsed laser delivers energy in brief, periodic bursts that allow stress to equalize between pulses. The short pulse duration prevents heat diffusion and thermal stress gradients, while the repetition rate is optimized to allow stress relaxation between cycles, resulting in uniform stress distribution across the bonded structure
Solution Approach 2:
The patent optimizes laser parameters including pulse width (ultra-short scale), repetition rate, and fluence to control the ablation process. By adjusting these parameters, the laser achieves controlled material removal with minimal stress concentration, preventing the uneven stress that plagues conventional dicing methods
3Productivity
If multiple wafers are diced simultaneously, then production efficiency can be improved, but thermal damage and debris increase
Solution Approach 1:
The ultra-short pulsed laser enables simultaneous dicing of multiple wafers by delivering energy in rapid periodic pulses. The short pulse duration and appropriate repetition rate prevent thermal accumulation even when processing multiple substrates concurrently, eliminating the trade-off between productivity and thermal damage
Solution Approach 2:
The patent combines multiple dicing operations into a single simultaneous laser processing step. By using the ultra-short pulsed laser with optimized parameters, multiple wafers can be diced at the same time without increasing thermal damage or debris generation, thereby improving production efficiency
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
The method achieves more uniform cross-sections, reduced damage, and increased usable area on wafers, with fewer scratches and less waste, while enabling simultaneous dicing of bonded wafers, thus improving production efficiency and reducing costs.
Implementation Method 1
A system and method for laser dicing bonded structures that form ablation structures within the wafers
Implementation Method 2
forming ablation structures within the wafers aligned vertically
Data Source
AI summary
Embodiments of systems and methods for dicing a bonded structure are provided. A method includes the following operations. First, a scan pattern can be determined for forming a series of ablation structures in the bonded structure. Relative positions between the series of ablation structures and a bonding interface of the bonded structure can then be determined. The bonding surface may be between a first wafer and a second wafer. At least one of one or more focal planes or a depth of focus of a laser beam may be determined based on the relative positions between the series of ablation structures and the bonding interface. Further, the laser beam may be determined. The laser beam has a series of pulsed lasers. Further, the laser beam may be moved in the bonded structure according to the scan pattern to form the series of ablation structures in the bonded structure.