Multi-layer Mask for Laser Plasma Substrate Dicing
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Solution Overview
Problem
Conventional dicing techniques for semiconductor substrates, such as scribing and sawing, face challenges with microcrack formation, delamination, and precise ablation depth control, especially for thin substrates, while plasma dicing is hindered by high implementation costs and masking issues due to substrate topography and metal processing limitations.
Innovation Solution
A multi-layered mask with a non-photodefinable laser light absorbing layer is used for laser scribing and subsequent plasma etching, allowing for precise singulation of ICs with a femtosecond laser and deep silicon plasma etch, improving edge quality and enabling easy mask removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional scribing or sawing is used for substrate dicing, then the dicing process can be performed with simple equipment, but microcrack formation and delamination occur reducing edge quality
Solution Approach 1:
The patent replaces mechanical scribing and sawing systems with a laser-based system. The laser beam ablates the substrate material along the scribe lines without mechanical contact, eliminating microcrack formation and delamination caused by mechanical stress. The laser parameters (wavelength, pulse duration, power) are optimized to achieve clean ablation edges while maintaining high precision singulation.
Solution Approach 2:
The laser dicing process utilizes phase transitions of substrate materials through controlled ablation. The laser energy causes localized heating and phase change (solid to vapor) at the scribe line, enabling precise material removal with clean edges. This phase transition mechanism allows for high-quality singulation without the mechanical damage associated with conventional methods.
2Manufacturing precision
If plasma dicing is implemented, then precise singulation can be achieved, but implementation cost increases due to standard lithography requirements
Solution Approach 1:
The patent extracts and removes the expensive standard lithography step from the plasma dicing process. Instead of using photolithography to pattern the resist, the invention directly applies plasma treatment through mask openings to define the scribe lines. This eliminates the need for photoresist coating, lithography exposure, and development steps, significantly reducing implementation cost while maintaining precise singulation capability.
Solution Approach 2:
The patent introduces a specialized mask structure as an intermediary between the plasma source and substrate. The mask with precisely positioned openings directs plasma flow to create scribe lines without requiring prior lithographic patterning. This intermediary approach enables direct plasma dicing with high precision while avoiding the costly lithography process.
3Adaptability or versatility
If plasma processing is used for copper metals in dicing, then through-silicon via formation is enabled, but product issues and throughput limits occur
Solution Approach 1:
The patent employs periodic pulsed plasma processing with controlled duty cycles to manage heat accumulation during copper dicing. The pulsed nature of the plasma allows for brief high-power intervals that effectively cut through copper and silicon, followed by cooling periods that prevent excessive heat buildup. This periodic action maintains high metal processing capability while avoiding throughput limitations caused by thermal management constraints.
4Manufacturing precision
If laser scribing is used for substrate dicing, then precise ablation depth control can be achieved, but microcrack formation occurs in thin substrates
Solution Approach 1:
The patent uses periodic pulsed laser operation with optimized pulse duration and repetition rate to control ablation depth while preventing microcrack formation in thin substrates. The pulsed delivery allows for precise energy deposition in each pulse, with inter-pulse cooling time that prevents excessive heat accumulation. This periodic action enables deep ablation control without generating the thermal stress that causes microcracks in thin substrate materials.
Solution Approach 2:
The patent dynamically adjusts laser parameters (power, pulse duration, scanning speed, repetition rate) based on substrate thickness and material properties. For thin substrates, the system uses lower power, shorter pulse durations, and reduced repetition rates to maintain precise ablation depth control while minimizing thermal stress. This dynamic parameter optimization prevents microcrack formation while achieving the required singulation precision.
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 method enhances the quality of scribed edges, reduces microcrack formation, and facilitates efficient singulation of ICs with improved die strength and throughput, overcoming the limitations of traditional dicing techniques.
Implementation Method 1
forming a non-photodefinable laser light absorbing mask over the semiconductor substrate
Implementation Method 2
The mask is patterned with a laser scribing process to provide a patterned mask with gaps, exposing regions of the substrate between the ICs
Implementation Method 3
The substrate may then be plasma etched through the gaps in the patterned mask to singulate the ICs into chips
Implementation Method 4
a base layer that is water-soluble to facilitate easy removal of the mask following the dicing process
Data Source
AI summary
Methods of dicing substrates having a plurality of ICs. A method includes forming a multi-layered mask comprising a laser energy absorbing, non-photodefinable topcoat disposed over a water-soluble base layer disposed over the semiconductor substrate. Because the laser light absorbing material layer is non-photodefinable, material costs associated with conventional photo resist formulations may be avoided. The mask is direct-write patterned with a laser scribing process to provide a patterned mask with gaps. The patterning exposes regions of the substrate between the ICs. Absorption of the mask layer within the laser emission band (e.g., UV band and/or green band) promotes good scribe line quality. The substrate may then be plasma etched through the gaps in the patterned mask to singulate the IC with the mask protecting the ICs during the plasma etch. The soluble base layer of the mask may then be dissolved subsequent to singulation, facilitating removal of the layer.