Laser-Assisted Substrate Separation via Dislocation Density Control
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Solution Overview
Problem
Conventional wafering processes for semiconductor materials, such as diamond-based or slurry-based wire sawing, result in material loss, surface damage, and the need for additional polishing and grinding steps due to cutting-gap losses and surface roughness, while existing kerf-less spalling methods lack control over wafer thickness and exhibit prominent Wallner lines, increasing surface roughness.
Innovation Solution
A method involving laser-assisted microcrack generation in donor substrates with inclined crystal lattice planes, where laser beams penetrate to create planar detachment regions, inducing compressive stresses that control crack propagation and reduce material loss by adjusting modification lines and laser energy based on dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If diamond-based or slurry-based wire sawing processes are used for wafering, then cutting and separation can be achieved, but material loss occurs and surface damage is caused requiring additional polishing and grinding steps
Solution Approach 1:
The patent replaces mechanical sawing processes (diamond-based or slurry-based wire sawing) with a stress-based spalling method that uses temperature-induced stresses to separate crystalline materials along crystal planes. This substitution eliminates the need for mechanical cutting, thereby preventing material loss and surface damage associated with traditional sawing processes.
Solution Approach 2:
The invention utilizes phase transitions through temperature changes to induce stresses in the crystal lattice. By heating the substrate to specific temperatures and then cooling it, thermal expansion and contraction create controlled stresses that cause the material to split along desired planes without mechanical contact, avoiding both material loss and surface damage.
2Loss of substance
If spalling processes are used to eliminate cutting-gap losses, then material loss is reduced, but control over wafer thickness is limited and Wallner lines increase surface roughness
Solution Approach 1:
The patent employs parameter changes by precisely controlling temperature variables during the spalling process. By adjusting heating temperature, heating rate, and cooling rate, the method achieves both complete separation (eliminating cutting-gap losses) and precise control over wafer thickness and crack propagation location, overcoming the limitations of conventional spalling.
Solution Approach 2:
The invention incorporates feedback mechanisms through real-time monitoring of temperature and stress conditions during the spalling process. This allows dynamic adjustment of process parameters to maintain precise control over crack propagation and wafer thickness, while preventing the formation of excessive Wallner lines that would compromise surface quality.
3Loss of substance
If spalling methods are used to separate crystalline materials, then cutting-gap losses are eliminated, but prominent Wallner lines develop increasing surface roughness and necessitating additional polishing steps
Solution Approach 1:
The patent utilizes parameter changes in temperature control to minimize Wallner line formation. By optimizing the heating and cooling rates, as well as the peak temperature held during spalling, the method achieves clean separation with reduced crack propagation dynamics, thereby minimizing surface roughness and Wallner lines while eliminating cutting-gap losses.
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 approach allows for precise modification of donor substrates, reducing material loss and surface roughness, enabling reliable division of substrates with varying qualities and minimizing the need for additional processing steps.
Implementation Method 1
Generating modifications in the interior of the donor substrate to form a detachment region in the interior of the donor substrate by means of a laser facility
Implementation Method 2
The modifications are more preferably generated by means of laser beams of the laser facility, where the laser beams with particular preference penetrate via the major surface into the donor substrate
Implementation Method 3
The modifications generate compressive stresses in the donor substrate, whereby the donor substrate, by virtue of the modification line or of the modification lines, undergoes cracking at least predominantly in the extent direction of the crystal lattice planes
Data Source
AI summary
A method includes: providing a semiconductor body having a generation plane and crystal lattice planes which intersect the generation plane at intersecting lines; generating modifications in the semiconductor body by multiphoton excitation and which are spaced apart from one another, the modifications altering a physical property of the semiconductor body so as to form subcritical cracks in the generation plane; and separating a solid-state layer from the semiconductor body by connecting the subcritical cracks in the generation plane.