Pressure-Guided Wafer Spalling for Planar Crack Control
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Solution Overview
Problem
Conventional wafering methods for semiconductor materials, such as diamond- or slurry-based wire sawing, result in kerf loss, surface damage, and require additional polishing and grinding steps, while stress-based spalling techniques face limitations in controlling wafer thickness and surface roughness due to prominent Wallner lines.
Innovation Solution
A method involving a stress generation layer on a donor substrate, subjected to thermal stress with a pressurizing element to control crack propagation, reducing vertical crack components and achieving more precise, planar crack progression, thereby minimizing material loss and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire sawing is used to cut wafers, then material can be separated, but kerf loss occurs and surface damage is created requiring additional polishing and grinding steps
Solution Approach 1:
The patent replaces the mechanical wire sawing system with a stress-based separation system. A stress generation layer is applied to the donor substrate, and controlled thermal stress is applied to induce crack propagation along the wafer interface, eliminating the need for mechanical cutting and thereby reducing kerf loss and surface damage
Solution Approach 2:
The patent utilizes thermal phase transitions to generate controlled stress. By heating the stress generation layer above its glass transition temperature and then cooling it, the material undergoes phase transitions that create thermal stress, driving crack propagation for wafer separation without mechanical contact
2Loss of substance
If spalling is used to separate wafers, then kerf loss is reduced, but Wallner lines are created on the surface increasing roughness
Solution Approach 1:
The patent applies local quality by creating a stress generation layer with specific properties (different thermal expansion coefficient) only at the separation interface. This localized stress generation enables controlled crack propagation along the wafer interface while minimizing surface disturbance and Wallner line formation on the final wafer surfaces
Solution Approach 2:
The patent changes the thermal parameters of the stress generation layer by heating it above its glass transition temperature and then cooling it. This parameter change creates controlled thermal stress that drives crack propagation while allowing better control over crack velocity and path, reducing Wallner line formation compared to conventional spalling
3Speed
If rapid crack propagation is used in spalling, then separation speed is increased, but control over crack path and wafer thickness is reduced
Solution Approach 1:
The patent implements feedback control by monitoring crack propagation in real-time and adjusting the cooling rate of the stress generation layer accordingly. This allows the system to maintain optimal crack velocity for both speed and precision, enabling control over crack path and wafer thickness while preserving rapid separation
Solution Approach 2:
The patent makes the stress generation system dynamic by allowing real-time adjustment of the cooling rate and stress application parameters during crack propagation. This dynamic control enables the system to adapt crack propagation speed and direction, achieving both high speed and precise control over wafer thickness and crack path
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 reduces material losses, shortens the splitting process, and minimizes surface roughness, allowing for more accurate detachment with reduced bending of the solid-state layer, enhancing the overall yield and reducing the need for additional processing steps.
Implementation Method 1
separating the solid-state slice from the donor substrate by subjecting the stress generation layer to thermal stress, which generates mechanical stresses in the donor substrate
Implementation Method 2
Cooling the bonded materials below the glass transition temperature of the polymer induces stresses that result in material splitting along a cracking plane
Implementation Method 3
the pressurizing element is pressed onto the stress generation layer during the subjecting of the stress generation layer to thermal stress, as a result of which a reduction in the crack propagation rate is achieved
Data Source
AI summary
The present invention relates to a method, according to claim 1, for separating at least one solid body layer (1), particularly a solid body disk, from a donor substrate (2). The method according to the invention comprises preferably at least the following steps: providing a donor substrate (2); producing or arranging a stress-producing layer (4) on a particularly flat surface (5) of the donor substrate (2) which axially defines the donor substrate (2); pressing at least one pressure application element (6) of a pressure application device (8) onto at least one pre-determined portion of the stress-producing layer (4), in order to press the stress-producing layer (4) onto the surface (5); separating the solid body layer (1) from the donor substrate (2) by thermally applying the stress-producing layer (4), thereby producing mechanical stress in the donor substrate (2), the mechanical stress creating a crack for separating a solid body layer (1), and the pressure application element (6) being pressed onto the stress-producing layer (4) during the thermal application of the stress-producing layer (4).