Wafer Division via Laser Ablation and Plasma Etching
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Solution Overview
Problem
The existing wafer processing methods using laser ablation to divide semiconductor wafers along division lines can cause thermal stress and cracks, leading to reduced die strength and potential damage to devices due to the brittleness of low-k films and metal films.
Innovation Solution
A method involving a protective member attachment, back grinding, modified layer formation, wafer supporting, protective film application, laser ablation for stacked member removal, and plasma etching to minimize damage and maintain die strength, including steps for attaching a protective member, grinding the wafer, forming a modified layer, supporting the wafer, applying a water-soluble resin for protection, removing the stacked member using a laser, and plasma etching to clean up damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser ablation is applied to remove stacked members (low-k film or metal film) on division lines, then the stacked member is removed and devices are separated, but thermal stress and cracks are generated causing reduction in die strength
Solution Approach 1:
A protective film made of water-soluble resin is applied as an intermediary layer between the laser beam and the stacked member. This mediator absorbs part of the laser energy and protects the underlying wafer and devices from direct laser-induced thermal stress and cracks, while still allowing the laser to remove the stacked member through the protective film
Solution Approach 2:
The protective film is applied in advance before laser ablation of the stacked member. This preliminary protective action prevents thermal damage to the wafer and devices before the laser processing occurs, allowing safe removal of the stacked member without compromising die strength
2Strength
If a protective film is applied before laser ablation, then thermal stress and cracks are minimized maintaining die strength, but an additional processing step is required
Solution Approach 1:
The protective film uses a water-soluble resin that can be removed by simple water washing, changing the removal method from complex chemical or mechanical processes to a simple parameter-based (solubility) removal. This minimizes the additional complexity introduced by the protective film step
3Ease of manufacture
If the wafer is divided along division lines with metal film (TEG), then devices are separated, but devices remain connected through the metal film preventing individual chip extraction
Solution Approach 1:
The protective film acts as an intermediary that allows the laser beam to pass through and ablate the metal film (TEG) on the division lines. This enables complete separation of devices by removing the conductive metal pathways that would otherwise connect adjacent devices, ensuring electrical independence of individual chips
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 divides wafers into individual device chips without reducing die strength by minimizing thermal stress and cracks, ensuring the integrity of the devices through careful layer formation and removal processes.
Implementation Method 1
applying a laser beam having a transmission wavelength to the wafer from the back side in the condition where the depth of focus of the laser beam coincides with a predetermined position in the thickness direction of the wafer, thereby forming a modified layer inside the wafer along each division line
Implementation Method 2
applying a laser beam to perform ablation to the stacked member formed on each division line, thereby removing the stacked member
Implementation Method 3
supplying an etching gas in a plasma state to the wafer, thereby removing damage due to the ablation
Data Source
AI summary
Disclosed herein is a wafer processing method including a stacked member removing step of applying a laser beam having an absorption wavelength to a stacked member through a protective film along each division line formed on the front side of a wafer, thereby performing ablation to remove the stacked member present on each division line, a dividing step of applying an external force to the wafer to divide the wafer into individual device chips along each division line where a modified layer is previously formed, and a plasma etching step of supplying an etching gas in a plasma state to the wafer from the front side thereof after performing the stacked member removing step or after performing the dividing step, thereby removing damage due to the ablation in the stacked member removing step.