Kerfless Wafer Separation Using Laser-Guided Crack Control
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Solution Overview
Problem
Conventional wafering processes for semiconductor materials result in kerf loss, surface roughness, and damage, necessitating additional polishing and grinding steps, while existing kerfless technologies face limitations in controlling wafer thickness and surface roughness due to Wallner lines.
Innovation Solution
A production facility that includes an analysis device for determining substrate properties, a laser device for generating modifications, and a separating device for mechanical stress induction to accurately separate wafers, with a data management system for precise process control and adaptation to individual substrate properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional sawing processes are used for wafering, then material can be divided into wafers, but kerf loss occurs and surface roughness increases requiring additional polishing steps
Solution Approach 1:
The patent replaces the mechanical diamond wire sawing system with a stress-based separation system. A stress layer is applied to the semiconductor ingot, and controlled stresses are induced to propagate cracks along desired planes, separating wafers without mechanical contact. This eliminates kerf loss entirely while maintaining manufacturing capability.
Solution Approach 2:
The patent changes the physical state and properties of materials involved in the separation process. By controlling temperature, stress, and the mechanical properties of the stress layer material, the separation process achieves clean cleavage without material loss. The stress layer material is selected and conditioned to match thermal expansion coefficients and provide controlled stress propagation.
2Ease of manufacture
If conventional sawing processes are used for wafering, then material can be divided into wafers, but surface roughness increases requiring additional polishing steps
Solution Approach 1:
The patent replaces mechanical sawing with stress-induced crack propagation. The crack follows crystallographic planes precisely, producing smooth, flat surfaces without the roughness generated by mechanical cutting. This eliminates the need for subsequent polishing steps while maintaining manufacturing efficiency.
Solution Approach 2:
The patent utilizes the inherent brittleness and crystal structure of semiconductor materials, which normally make them difficult to process, as an advantage. By inducing controlled cracks that follow crystal planes, the material's natural properties produce perfectly flat, smooth surfaces ideal for semiconductor fabrication, converting the harmful brittleness into a beneficial separation mechanism.
3Loss of substance
If spalling processes are used for kerfless wafering, then material loss is reduced, but Wallner lines appear on the surface increasing surface roughness
Solution Approach 1:
The patent applies local quality by using a stress layer with specific local properties that interact differently with various regions of the semiconductor ingot. The stress layer is positioned and configured to generate controlled stress distribution, creating separation planes that avoid the random crack propagation causing Wallner lines, while maintaining kerfless separation.
Solution Approach 2:
The patent introduces a stress layer as an intermediary between the external stress application and the semiconductor material. This intermediate layer mediates the stress transmission, distributing it uniformly to produce clean, controlled cracks without the surface defects (Wallner lines) that occur in direct spalling processes. The stress layer acts as a buffer that eliminates harmful surface patterns.
4Manufacturing precision
If individual substrate properties are measured and process parameters are adapted, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent implements feedback by measuring individual substrate properties (such as crystal orientation, stress characteristics, and geometric parameters) and using this information to adjust process parameters in real-time. The system continuously monitors separation progress and adapts stress application, temperature, and other parameters to achieve precise wafer separation for each unique substrate, improving manufacturing precision through closed-loop control.
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 enables efficient cleavage of wafers with reduced material loss and surface roughness, achieving low-stress wafers within tight geometric tolerances and improving overall production facility effectiveness by optimizing process management and tool synchronization.
Implementation Method 1
a laser device for generating modifications inside the donor substrates in order to form a separating region inside the respective donor substrate
Implementation Method 2
generating modifications inside the donor substrates... donor substrates comprising a semiconductor material, in particular silicon carbide
Implementation Method 3
a separating device for generating mechanical stresses inside the respective donor substrate in order to initiate and/or guide a crack in order to separate respectively at least one wafer from a donor substrate
Implementation Method 4
at least one analysis device for determining at least one individual property, in particular the doping, of the respective donor substrate
Data Source
AI summary
A method for separating wafers from donor substrates incudes: determining at least one individual property of a respective donor substrate, the at least one individual property including doping and/or crystal lattice dislocations of the respective donor substrate; generating donor substrate process data for the respective donor substrate, the donor substrate process data including analysis data of the analysis device, the analysis data describing the at least one individual property of the respective donor substrate; generating, via a laser device, modifications inside the respective donor substrate to form a separating region inside the respective donor substrate, the laser device being operable as a function of the donor substrate process data of the respective donor substrate; and generating mechanical stresses inside the respective donor substrate to initiate and/or guide a crack for separating at least one wafer from the respective donor substrate.