Laser-Cleaved Off-Angle Ingot Wafer Separation With Flatter Surfaces
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Solution Overview
Problem
The existing wafer production methods face inefficiencies due to variations in release location, leading to rough surfaces and increased grinding or polishing requirements, and instability in the separation process, which can result in failure to release the plate-like object from the ingot.
Innovation Solution
A wafer production method involving the formation of a separation layer on the ingot using a laser beam, with the ingot's c-axis oriented at an off-angle, allowing for precise separation and subsequent planarization of the wafer surface, reducing the physical load required and minimizing surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic vibration is applied to release the plate-like object from the ingot, then the separation process can be performed, but the release location varies in the height direction leading to rough surfaces
Solution Approach 1:
A release start point is created in advance by emitting a laser beam to form a reformed layer at a predetermined depth from the outer surface of the ingot. This preliminary action ensures that when ultrasonic vibration is subsequently applied, the separation occurs consistently from this pre-defined location, eliminating variations in release position and preventing rough surfaces.
2Productivity
If conventional wafer production method is used, then separation can be achieved, but increased grinding or polishing allowance is required due to rough surfaces
Solution Approach 1:
The release start point is formed in advance using laser irradiation to create a reformed layer at the precise depth corresponding to the target wafer thickness. This preliminary preparation ensures that subsequent separation produces a flat surface, minimizing or eliminating the need for additional grinding or polishing operations, thereby improving production efficiency.
3Measurement precision
If laser beam is emitted to form separation layer, then precise separation depth can be achieved, but the ingot must have specific transmittance properties
Solution Approach 1:
The laser beam wavelength is selected to match the transmittance characteristics of the ingot material. By choosing a wavelength to which the ingot is transparent, the laser energy penetrates to the desired depth and forms the reformed layer precisely at the target position, achieving accurate separation depth control while adapting to the specific material properties of the ingot.
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 enhances production efficiency by stabilizing the separation process, reducing the roughness of the separated surface, and minimizing the grinding or polishing allowance, thereby improving the overall efficiency of wafer production.
Implementation Method 1
a separation layer formation step of emitting a laser beam to one of end surfaces of the ingot opposed to each other in height direction of the ingot to form a separation layer at a depth from the end surface of the ingot
Implementation Method 2
The separation of the wafer precursor from the ingot is achieved by applying a physical load in a single direction to an end of the ingot facing in the off-angle direction
Data Source
AI summary
A wafer production method for producing a wafer from an ingot oriented to have a c-axis inclined in an off-angle direction at an off-angle more than zero degree From a central axis includes steps of emitting a laser beam to a top surface that is one of end surfaces of the ingot opposed to each other in height direction thereof to form a separation layer at a depth from the top surface of the ingot which corresponds to a thickness of the wafer, applying a physical load in a single direction to a first end that is one of ends of the ingot which are opposed to each other in an off-angle direction to remove a wafer precursor from the ingot at the separation layer, and planarizing a major surface of a removed object derived by separating the wafer precursor from the ingot at the separation layer, thereby forming a wafer. The ingot has a given degree of transmittance to the laser beam. The wafer precursor is created by a portion of the ingot between the top surface of the ingot and the separation layer.