SiC Wafer Separation Using Dual-Density Ultrasonic Vibration
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Solution Overview
Problem
The existing methods for producing wafers from hexagonal single-crystal SiC ingots are inefficient due to high ingot discard rates and difficulty in cutting, leading to poor productivity and economic issues, especially when using wire saws, and previous laser-based techniques face challenges in separating wafers along formed separation layers.
Innovation Solution
A wafer producing method that involves forming a separation layer inside the ingot using a laser beam, followed by applying ultrasonic vibrations at different densities to break the separation layer, allowing for efficient separation of wafers from the ingot, with the first ultrasonic vibration applied to a specific area at high density and the second applied to the entire area at lower density to form a fully broken portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wire saw is used to slice the ingot, then the ingot can be divided into wafers, but 70% to 80% of the ingot is discarded causing poor economy
Solution Approach 1:
The invention divides the ingot into multiple wafers by forming separation layers at predetermined intervals using laser processing, allowing sequential extraction of wafers without discarding the bulk material. This segmentation approach enables utilization of nearly the entire ingot volume, reducing discard rate from 70-80% to minimal amounts between individual wafers.
Solution Approach 2:
The invention performs preliminary laser processing to form separation layers inside the ingot before actual wafer extraction. By pre-establishing these separation planes at desired depths, the subsequent wafer extraction becomes straightforward and efficient, eliminating the need for time-consuming wire saw cutting while maximizing material utilization.
2Productivity
If wire saw is used to cut the hexagonal single-crystal SiC ingot, then the ingot can be sliced into wafers, but considerable time is required reducing productivity
Solution Approach 1:
The invention replaces the mechanical wire saw cutting system with a laser-based processing system. The laser beam forms separation layers through optical energy absorption and thermal effects, eliminating the slow mechanical cutting process. This substitution dramatically reduces processing time while enabling sequential wafer extraction from the same ingot.
Solution Approach 2:
The invention changes the processing parameters from mechanical cutting forces to laser energy parameters (power, pulse duration, scanning speed). By controlling laser parameters, separation layers are formed rapidly at precise depths, enabling fast wafer production without the time-consuming mechanical cutting process.
3Loss of substance
If laser beam is used to form separation layer inside the ingot, then ingot discard is reduced, but it is not easy to separate the wafer from the ingot along the separation layer
Solution Approach 1:
The invention applies ultrasonic vibration to the ingot along the formed separation layers to facilitate wafer extraction. The mechanical vibration energy disrupts the bonding at the separation interfaces, enabling easy separation of wafers from the ingot without compromising the integrity of the separation layers formed by laser processing.
Solution Approach 2:
The invention introduces ultrasonic vibration as an intermediary mechanism between the laser-formed separation layers and the wafer extraction process. This intermediary action weakens the bonding at separation planes, making it easy to extract wafers while maintaining the advantages of reduced material discard achieved through laser processing.
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 ingot discard and facilitates easy and efficient separation of wafers from the ingot, improving productivity and reducing economic losses compared to traditional wire saw methods.
Implementation Method 1
setting a focal point of a laser beam having a transmission wavelength to the ingot inside the ingot at a predetermined depth from one end surface of the ingot, the predetermined depth corresponding to the thickness of the wafer to be produced, and next applying the laser beam to the ingot
Implementation Method 2
a first ultrasonic vibration applying step of applying ultrasonic vibration to a given area of the ingot at a first density to thereby form a partially broken portion where a part of the separation layer is broken
Data Source
AI summary
A wafer producing method for producing a wafer from an ingot, the ingot being previously formed with a separation layer along which the wafer is to be separated from the ingot. The wafer producing method includes a first ultrasonic vibration applying step of applying ultrasonic vibration to a given area of the ingot at a high density to thereby form a partially broken portion where a part of the separation layer is broken, a second ultrasonic vibration applying step of applying the ultrasonic vibration to the whole area of the ingot larger than the given area at a low density, after performing the first ultrasonic vibration applying step, thereby forming a fully broken portion where the separation layer is fully broken in such a manner that breaking starts from the partially broken portion, and a separating step of separating the wafer from the ingot along the fully broken portion.