Ultra-Thin Wafer Dicing via Laser Ablation and Plasma Damage Removal
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Solution Overview
Problem
Conventional dicing techniques for semiconductor substrates, such as mechanical scribing and sawing, face challenges with microcrack formation, delamination, and precise control of kerf width and ablation depth, especially for thin substrates, while plasma dicing is limited by costly lithography and masking issues.
Innovation Solution
A hybrid method combining femtosecond laser scribing and plasma etching, where a patterned mask is used to expose regions between ICs, allowing for precise ablation and subsequent plasma etching to improve die strength and remove scribe damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical scribing or sawing is used for dicing thin substrates, then the dicing process can be performed with conventional equipment, but microcrack formation, delamination, and poor process quality occur
Solution Approach 1:
The patent replaces mechanical scribing and sawing systems with a laser-based ablation system. The laser beam ablates the substrate material through photothermal and photomechanical effects, eliminating mechanical contact that causes microcracks and delamination. The laser parameters (wavelength, pulse duration, power) are optimized to achieve clean ablation of thin substrates without mechanical stress.
Solution Approach 2:
The patent utilizes controlled changes in laser parameters (wavelength, pulse duration, energy density) to optimize the ablation process for thin substrates. By adjusting these parameters, the laser interaction with the substrate material is controlled to achieve precise kerf width and minimal thermal damage, improving process quality compared to mechanical methods.
2Reliability
If plasma dicing is used, then dicing can be performed without mechanical contact, but lithography costs and masking complexity increase
Solution Approach 1:
The patent extracts and eliminates the lithography and masking steps from the plasma dicing process. Instead of using photoresist patterns to define dicing streets, the laser system directly ablates the substrate along predetermined paths. This removes the complex lithography apparatus and masking materials while maintaining the non-contact advantage of plasma processing.
Solution Approach 2:
The laser beam serves as an intermediary that directly transfers energy to the substrate for ablation, replacing the complex plasma-generating apparatus and masking system. The laser provides a simpler, more direct energy transfer mechanism that achieves similar non-contact material removal without the overhead of plasma equipment and masking processes.
3Device complexity
If conventional dicing methods are used on thin substrates, then the process is simple, but precise kerf width control and ablation depth control are difficult to achieve
Solution Approach 1:
The patent implements feedback control in the laser ablation process by monitoring ablation characteristics (e.g., plasma emission, acoustic signals) and adjusting laser parameters in real-time. This feedback mechanism maintains precise kerf width control even as substrate conditions vary, achieving manufacturing precision that exceeds conventional methods while keeping the overall process relatively simple.
Solution Approach 2:
The patent uses periodic pulsed laser action instead of continuous irradiation. The pulsed regime allows heat diffusion between pulses, preventing excessive thermal accumulation that would broaden the kerf. By optimizing pulse duration and repetition rate, precise kerf width control is achieved while maintaining a relatively simple laser system configuration.
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 method effectively singulates ICs with minimal thermal damage, improving die strength and reducing microcrack formation, while avoiding the costs and complexities of traditional lithography and masking processes.
Implementation Method 1
ablating, with the laser scribing process, the entire thickness of the substrate within the gaps in the patterned mask to singulate the ICs
Implementation Method 2
plasma etching to improve die strength and remove scribe damage
Data Source
AI summary
Methods of dicing substrates having a plurality of ICs. A method includes forming a mask, patterning the mask with a femtosecond laser scribing process to provide a patterned mask with gaps, and ablating through an entire thickness of a semiconductor substrate to singulate the IC. Following laser-based singulation, a plasma etch is performed to remove a layer of semiconductor sidewall damaged by the laser scribe process. In the exemplary embodiment, a femtosecond laser is utilized and a 1-3 μm thick damage layer is removed with the plasma etch. Following the plasma etch, the mask is removed, rendering the singulated die suitable for assembly/packaging.