Wafer Separation Along Crack Layers to Reduce Surface Tension
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Solution Overview
Problem
The application of ultrasonic waves through a liquid layer during the separation of wafers from ingots can cause strong resistive forces due to surface tension, leading to a higher probability of breaking either the wafer or the ingot.
Innovation Solution
A method involving the formation of separation layers with modified areas and cracks in the ingot, followed by the application of ultrasonic waves through a liquid layer, and then pulling the wafer and ingot apart in the direction of the separation layers, reducing the resistive forces by aligning the separation process with the direction of the separation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultrasonic waves are applied via a layer of liquid to the ingot to separate the wafer from the ingot, then the separation process can be performed, but strong resistive forces caused by surface tension act on the wafer and ingot, making them more probable to be broken
Solution Approach 1:
The invention forms separation layers with pre-defined crack patterns in the ingot before the ultrasonic wave application. These separation layers are created by laser processing that introduces controlled modifications and cracks, which then guide the ultrasonic wave propagation and fracture paths during separation, reducing the forces needed and preventing unexpected breakage
Solution Approach 2:
The invention introduces a liquid layer as an intermediary medium between the ultrasonic wave source and the ingot. This liquid layer serves as a coupling medium that transmits ultrasonic waves effectively while also reducing direct contact forces, and the pulling direction is optimized to align with the separation layers to minimize surface tension resistance
2Productivity
If the wafer and ingot are pulled apart in a direction perpendicular to the interface between them, then separation can be achieved, but strong resistive forces from surface tension act on the wafer and ingot, increasing the likelihood of breaking
Solution Approach 1:
The invention pre-forms separation layers with specific crack patterns using laser processing before the actual separation operation. These pre-formed separation layers create preferred fracture paths that guide the separation process, allowing the wafer to be separated along predetermined planes with reduced force requirements and minimized risk of uncontrolled breakage
Solution Approach 2:
The invention changes the pulling direction parameter from perpendicular to the interface to parallel with the separation layers. This parameter change in the separation direction, combined with the pre-formed crack patterns, reduces the resistive forces from surface tension and aligns the separation process with the weakest planes in the material structure
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 reduces the likelihood of breaking the wafer or ingot during separation by minimizing the resistive forces acting on them due to surface tension, ensuring a more controlled and efficient separation process.
Implementation Method 1
a focused spot of a laser beam having a wavelength transmittable through the material of the ingot
Implementation Method 2
forming, in the ingot, a plurality of separation layers each including a modified area and cracks developed from the modified area
Implementation Method 3
an ultrasonic wave applying step of applying ultrasonic waves via a layer of liquid to the ingot to separate the ingot along the separation layers
Implementation Method 4
strong resistive forces caused by the surface tension of the layer of liquid act on the wafer and the ingot
Data Source
AI summary
After ultrasonic waves have been applied via a layer of liquid to an ingot for separating the ingot along separation layers formed therein to thereby produce a wafer from the ingot, the wafer and the ingot are moved relatively to each other along a direction in which the separation layers extend, thereby pulling apart the wafer and the ingot from each other.