Laser Modification Lines for Kerf-Loss Wafer Separation
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Solution Overview
Problem
Conventional wafering methods for semiconductor materials result in kerf losses, surface damage, and increased processing costs due to kerf loss and surface roughness, with spalling techniques limited in control over wafer thickness and prone to prominent Wallner lines that require additional polishing steps.
Innovation Solution
A method involving a donor substrate with inclined crystal lattice planes, where laser radiation is used to create subcritical cracks by changing material properties, allowing for controlled detachment of solid-state layers with reduced material loss and surface roughness, using laser beams to generate linear designs that limit crack propagation along specific crystal planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If diamond- or slurry-based wire sawing processes are used for wafering, then the semiconductor material can be cut into wafers, but kerf loss occurs and surface damage is created requiring additional polishing steps
Solution Approach 1:
The patent replaces mechanical wire sawing with a laser-based system that uses light to induce subcritical cracks in the crystal lattice. The laser radiation creates modification lines along crystal planes, and mechanical stress then propagates these cracks to separate wafers without mechanical contact, eliminating kerf loss and surface damage associated with diamond or slurry sawing
Solution Approach 2:
The laser pre-modifies the crystal lattice by creating subcritical cracks and modification lines along crystal planes before the actual wafer separation. This preliminary action weakens the crystal structure in a controlled manner, allowing subsequent mechanical stress to cleanly propagate cracks along predetermined paths without requiring forceful mechanical cutting
2Productivity
If diamond- or slurry-based wire sawing processes are used for wafering, then the semiconductor material can be cut into wafers, but surface roughness is created requiring additional polishing steps
Solution Approach 1:
The patent replaces mechanical wire sawing with a laser-based system that uses light to induce subcritical cracks in the crystal lattice. The laser radiation creates modification lines along crystal planes, and mechanical stress then propagates these cracks to separate wafers without mechanical contact, eliminating surface roughness and damage associated with diamond or slurry sawing
Solution Approach 2:
The laser applies energy locally and selectively to specific crystal planes, creating modification lines only where needed for wafer separation. This localized modification preserves the high quality of surrounding crystal regions, enabling clean wafer separation without the widespread surface damage caused by mechanical sawing
3Loss of substance
If conventional spalling processes are used to separate solid-state layers, then kerf losses are reduced, but control over wafer thickness and crack propagation location is limited
Solution Approach 1:
The laser creates localized modification lines at precisely controlled depths and positions within the crystal lattice. By adjusting laser parameters such as power, pulse duration, and focal depth, the modification lines can be positioned exactly where desired to control crack propagation and achieve precise wafer thickness, overcoming the limited control of conventional spalling
Solution Approach 2:
The patent utilizes adjustable laser parameters (power, pulse duration, wavelength, focal position) to precisely control the depth and location of modification lines. By changing these parameters, the crack propagation path and resulting wafer thickness can be accurately controlled, providing manufacturing precision that conventional spalling cannot achieve
4Loss of substance
If conventional spalling processes are used to separate solid-state layers, then kerf losses are reduced, but prominent Wallner lines are created on the surface requiring additional polishing steps
Solution Approach 1:
The patent replaces conventional mechanical spalling with a laser-induced crack propagation system. The laser creates modification lines that guide crack propagation along crystal planes without the uncontrolled stress fields that generate Wallner lines in conventional spalling. The result is clean wafer separation without prominent surface patterns
Solution Approach 2:
The laser-induced modification lines act as intermediaries that control crack propagation paths. These modification lines provide a predetermined trajectory for crack growth along crystal planes, preventing the uncontrolled crack propagation and Wallner line formation that occurs in conventional spalling processes
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 achieves lower material losses and reduced surface roughness, enabling more precise control over wafer thickness and minimizing the need for additional polishing steps, thus improving the efficiency and cost-effectiveness of semiconductor manufacturing.
Implementation Method 1
introducing laser radiation from the laser into the interior of the solid-state body via the main surface to change the material properties of the solid-state body in the region of at least one laser focus
Implementation Method 2
wherein the changed material property results in tearing of the donor substrate in the form of subcritical cracks
Data Source
AI summary
The present invention therefore relates to a method for separating at least one solid body layer (2) from a donor substrate (1). According to the invention, the method preferably comprises at least the steps of: providing the donor substrate (1), wherein the donor substrate (1) has crystal lattice planes (6) which are inclined in relation to a planar main surface (8), wherein the main surface (8) delimits the donor substrate (1) in the longitudinal direction of the donor substrate (1) on one side, wherein a crystal lattice plane normal is inclined in relation to a main surface normal in a first direction, providing at least one laser, introducing laser radiation of the laser into the interior of the donor substrate (1) via the main surface (8) for changing the material properties of the donor substrate (1) in the region of at least one laser focus, wherein the laser focus is formed by laser beams of the laser which are emitted by the laser, wherein the change in the material property by changing the point of entry of the laser radiation into the donor substrate (1) forms a linear shape (103), wherein the changes in the material property are generated on at least one generating plane (4), wherein the crystal lattice planes (6) of the donor substrate (1) are oriented in an inclined manner in relation to the generating plane (4), wherein the linear design (103) is inclined in relation to a sectional line (10) which is produced at the interface between the generating plane (4) and the crystal lattice plane (6), wherein, owing to the changed material property, the donor substrate (1) tears in the form of subcritical cracks, separating the solid body layer (2) by introducing an external force into the donor substrate (1) for connecting the subcritical crack or so much material on the generating plane (4) being changed by means of the laser radiation that the solid body layer (2) becomes detached from the donor substrate (1) with connection of the subcritical crack.