Laser Spalling of Solid Layers With Crack-Guided Wafer Separation
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Solution Overview
Problem
Traditional semiconductor wafering methods using diamond or slurry-based wire sawing result in material loss, surface roughness, and subsurface damage, necessitating additional polishing and grinding steps, while stress-based spalling techniques face limitations in controlling wafer thickness and surface roughness due to Wallner lines.
Innovation Solution
A laser-assisted spalling method that uses short laser pulses with high numerical aperture to define a crack propagation plane, followed by thermal stress generation with a polymer layer, allowing for precise separation of semiconductor layers with reduced surface roughness and material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If diamond or slurry-based wire sawing is used for wafering, then material can be separated, but kerf loss occurs and surface roughness and subsurface damage are generated
Solution Approach 1:
The patent replaces the mechanical wire sawing system with a laser-based system. Laser beams create modifications inside the solid to define a detachment region, eliminating the need for mechanical cutting. This substitution eliminates kerf loss and avoids the surface roughness and subsurface damage caused by mechanical contact between the wire and material.
Solution Approach 2:
The patent applies preliminary laser modifications inside the solid material before separation occurs. These modifications define the detachment region and prepare the material for clean separation. By pre-defining the separation plane through laser-induced modifications, the process avoids the need for subsequent polishing and grinding steps that would otherwise be required to correct surface damage.
2Productivity
If conventional spalling is used to separate layers, then material separation occurs, but additional polishing or grinding steps are required
Solution Approach 1:
The patent merges the laser modification step and the separation step into a unified process. The laser both defines the detachment region and initiates the separation process in one operation, eliminating the need for separate polishing or grinding steps that would otherwise be required to correct surface damage from conventional spalling.
Solution Approach 2:
The patent replaces the mechanical polishing and grinding steps with a laser-based modification process. The laser creates precise modifications inside the material that define the detachment region, eliminating the need for subsequent mechanical surface correction steps and reducing the overall process complexity.
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 achieves efficient separation with minimal surface roughness (Ra < 1 µm) and reduced material loss, eliminating the need for extensive polishing and grinding, thereby improving the efficiency and accuracy of semiconductor wafer production.
Implementation Method 1
creating modifications inside the solid with a laser beam
Implementation Method 2
Cooling the bonded materials below the polymer's glass transition temperature induces stresses that lead to material separation
Data Source
Figure 1
Figure 2a~2b
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AI summary
The present invention relates to a method for separating at least one solid layer from a solid body (1), wherein the modifications (2) define a crack guidance area (4) for guiding a crack to separate a solid component, in particular a solid layer, from the solid body (1).The present invention comprises at least the following steps: moving the solid (1) relative to a laser application device, successively generating laser beams (10) by means of the laser application device to generate at least one modification (2) each, wherein inhomogeneities of the solid (1) in the area of the applied surface and/or in the area of the applied volume of the solid (1) are compensated by adjusting the laser application device, separating the solid layer from the solid (1), and removing material from the solid (2), in particular to create a circumferential depression, wherein the material removal takes place in the longitudinal direction of the solid (1).