Silicon Wafer Formation via Internal Laser Separation
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Solution Overview
Problem
The existing methods for slicing silicon ingots to form wafers result in significant material wastage, with approximately 60% to 70% of the ingot being discarded, leading to poor productivity in silicon wafer formation.
Innovation Solution
A silicon wafer forming method that involves cutting the silicon ingot into block ingots, planarizing the end face, forming a separation layer using a laser beam with a focal point inside the ingot, and separating the wafers from this layer, along with an optional production history marking, to reduce material loss and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cutting machine such as a wire saw and an inner saw is used to slice the silicon ingot, then the silicon wafer can be formed, but the margin for slicing is large and most part (approximately 60% to 70%) of the silicon ingot is discarded
Solution Approach 1:
The patent replaces the mechanical cutting system (wire saw, inner saw) with a laser-based system. The laser beam forms a separation layer inside the silicon ingot without requiring large mechanical margins, thereby reducing material waste while maintaining wafer formation capability.
Solution Approach 2:
The patent changes the wavelength parameter of the laser beam to one that is transmitted through silicon, enabling the laser to penetrate and form a separation layer deep inside the ingot. This parameter change allows precise internal separation without the need for large external cutting margins.
2Productivity
If a cutting machine such as a wire saw and an inner saw is used to slice the silicon ingot, then the silicon wafer can be formed, but the productivity is poor due to large material wastage
Solution Approach 1:
The patent replaces the mechanical cutting system with a laser-based system that can process the silicon ingot more efficiently. The laser method reduces processing time and material waste, thereby improving overall productivity in wafer formation.
Solution Approach 2:
The patent performs preliminary action by forming the separation layer inside the silicon ingot before actual wafer separation. This internal pre-positioning of the separation layer allows for more efficient subsequent processing and reduces the need for large margins, improving productivity.
3Loss of substance
If a laser beam with transmitted wavelength is applied with focal point inside the block ingot, then the separation layer can be formed with reduced margin, but the process complexity increases
Solution Approach 1:
The patent uses the laser beam as an intermediary to transfer energy into the silicon ingot. The laser wavelength is specifically chosen to be transmitted through silicon, allowing the energy to reach the focal point inside the ingot and form the separation layer without requiring complex mechanical cutting apparatus.
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 significantly reduces the margin for slicing, allowing for more efficient formation of silicon wafers from the ingot, thereby improving productivity and enabling the formation of wafers with minimal waste.
Implementation Method 1
applying a laser beam of such a wavelength as to be transmitted through silicon to the block ingot, with a focal point of the laser beam positioned in the inside of the block ingot at a depth from the end face of the block ingot corresponding to the thickness of the wafer to be formed
Implementation Method 2
applying a laser beam of such a wavelength as to be transmitted through silicon to the block ingot, with a focal point of the laser beam positioned in the inside of the block ingot
Data Source
AI summary
A silicon wafer forming method includes: a block ingot forming step of cutting a silicon ingot to form block ingots; a planarizing step of grinding an end face of the block ingot to planarize the end face; a separation layer forming step of applying a laser beam of such a wavelength as to be transmitted through silicon to the block ingot, with a focal point of the laser beam positioned in the inside of the block ingot at a depth from the end face of the block ingot corresponding to the thickness of the wafer to be formed, to form a separation layer; and a wafer forming step of separating the silicon wafer to be formed from the separation layer.