GaN Wafer Separation Layer Processing for Low-Loss Throughput
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Solution Overview
Problem
The existing methods for manufacturing gallium nitride wafers using a wire saw result in low productivity due to high discard rates, while high-power laser beam methods increase costs and risk damage to optical components, and low-power laser methods reduce throughput.
Innovation Solution
A wafer manufacturing method using a pulsed laser beam with a high repetition frequency and controlled pulse energy to form a separation layer within the ingot, allowing for efficient wafer separation with reduced discard rates and increased throughput without the need for high-power lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a wire saw is used to cut wafers from the ingot, then the cutting process can be performed, but the discard rate increases to approximately 2/3 of the ingot volume and productivity decreases
Solution Approach 1:
The patent replaces the mechanical wire saw cutting system with a laser beam processing system. The laser beam forms a separation layer within the ingot by irradiating it, and the wafer is then separated using this separation layer as a starting point. This substitution eliminates the need for mechanical cutting, thereby reducing the discard rate from 2/3 to a much lower value while maintaining or improving productivity.
Solution Approach 2:
The patent changes the processing parameters by using a laser beam with a wavelength transmittable through the ingot material. By controlling the laser beam parameters (wavelength, power, scanning speed) and the relative movement between the laser beam and ingot, the separation layer is formed at a controlled depth, enabling efficient wafer separation with minimal material loss.
2Productivity
If the peak power of the laser beam is raised to improve throughput, then the separation layer can be formed faster, but the laser oscillator size increases and optical components are damaged
Solution Approach 1:
The patent uses a pulsed laser beam instead of a continuous high-power laser beam. The pulsed operation allows the laser to deliver high peak power in short bursts followed by cooling periods, enabling the formation of the separation layer efficiently without requiring a continuously high-power laser oscillator. This reduces the size and cost of the laser system while maintaining throughput.
Solution Approach 2:
The patent achieves continuous processing by rapidly scanning the laser beam across the ingot surface or by moving the ingot under the laser beam. The pulsed laser operates continuously in terms of scanning coverage, forming the separation layer along the entire required path without interruption, thereby maintaining high throughput without needing excessive peak power at any single point.
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
The method effectively reduces discard rates and improves wafer productivity while preventing a decrease in throughput, even with lower power laser usage, and minimizes damage to optical components.
Implementation Method 1
forming a separation layer including a plurality of modified regions within the workpiece by moving the workpiece and a condensing point of a pulsed laser beam having a wavelength transmittable through the workpiece relative to each other at a predetermined speed along a processing feed direction in a state in which the workpiece is irradiated with the pulsed laser beam from another surface side of the workpiece
Data Source
AI summary
A wafer manufacturing method includes a separation layer forming step of forming a separation layer including a plurality of modified regions within a workpiece by moving the workpiece and a condensing point of a pulsed laser beam having a wavelength transmittable through the workpiece relative to each other at a predetermined speed along a processing feed direction in a state in which the workpiece is irradiated with the laser beam, and the condensing point of the laser beam is located at a predetermined depth position of the workpiece, and a separating step of separating a wafer from the workpiece with the separation layer as a starting point, in the separation layer forming step, a repetition frequency of the laser beam is set according to pulse energy and the relative predetermined speed between the workpiece and the condensing point such that the separation layer can be formed.