Semiconductor Wafer Peeling Layer for Stable Crack Propagation
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Solution Overview
Problem
Existing wafer production methods face issues such as sagging or chipping during grinding and polishing, leading to stress concentration and unintended cracks in the outer peripheral parts of semiconductor ingots, which lowers material yield and destabilizes the peeling process.
Innovation Solution
A method involving the application of a tensile stress to a semiconductor ingot with a pre-formed peeling layer to concentrate stress inside the outer peripheral edge, initiating cracks from a controlled starting point within the ingot, using a peeling jig to separate wafers stably and efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pressing mechanism is used to separate wafers from the ingot, then the wafer separation process can be performed, but torsional stress is generated on the ingot causing unintended cracks in the outer peripheral part
Solution Approach 1:
The patent replaces the conventional pressing mechanism that applies torsional stress with a laser beam system that creates controlled modifications. The laser beam writes modification patterns on the ingot surface, and then a peeling mechanism separates wafers along these controlled modification lines, avoiding the harmful torsional stress of traditional pressing methods
Solution Approach 2:
The patent changes the stress application method from mechanical torsional stress to controlled laser-induced modification. By using laser parameters (wavelength, power, scanning speed) to create specific modification patterns, the process achieves wafer separation without generating harmful stress concentrations in the outer peripheral regions
2Manufacturing precision
If griding or polishing processes are applied to the ingot, then the ingot surface can be prepared, but stress concentrates at sagging or chipped parts causing cracks
Solution Approach 1:
The patent applies laser modification before the peeling process to create controlled stress distribution patterns. This preliminary action prepares the ingot with predefined separation lines that guide subsequent wafer removal, preventing stress from concentrating at random defect locations
Solution Approach 2:
The patent creates localized modification patterns in specific regions of the ingot using laser writing. These local modifications concentrate the necessary stress changes only where needed for separation, while leaving other regions unaffected and avoiding stress concentration at unwanted locations
3Productivity
If cracks propagate from unintended starting points in the outer peripheral part, then material yield decreases, but the peeling process can still proceed
Solution Approach 1:
The patent introduces laser-induced modification patterns as an intermediary between the ingot structure and the peeling process. These modification patterns serve as controlled starting points for crack propagation, ensuring that separation occurs at predetermined locations rather than at random defect sites, thereby preserving material yield
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 enhances the stability and efficiency of the peeling process by controlling crack propagation from a stress-concentrated region, reducing material waste and improving yield by avoiding unintended cracks.
Implementation Method 1
a converging point of a laser beam having a wavelength to which the ingot, fixed on the supporting table, has transparency, is positioned at a depth position corresponding to a wafer thickness from a surface of the ingot, and the laser beam is irradiated on the surface
Implementation Method 2
forming, with an application of the tensile stress to the peeling object, a stress-concentrated region in the peeling layer which is positioned inside an outer peripheral edge (13, 23) in a radial direction of which the center is a center axis (CL) orthogonal to the major surface of the single crystal body; and propagating cracks from the stress-concentrated region as a starting point
Data Source
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AI summary
A method for manufacturing a semiconductor wafer includes steps of: preparing a peeling object (30) including a single crystal body (1, 2) of a semiconductor having a pair of major surfaces composed of front and back surfaces, the peeling object having a peeling layer (31) provided along at least one of the major surfaces; applying a tensile stress to the peeling object (30) to cause a first major surface and a second major surface to be separated from each other; forming a stress-concentrated region in the peeling layer (31) positioned inside an outer peripheral edge (13, 23) in a radial direction of which the center is a center axis (CL) orthogonal to the major surface; and propagating cracks from the stress-concentrated region as a starting point, thereby peeling between a first side portion and a second side portion of the peeling object (30) having the peeling layer (31) interposed therebetween in a direction parallel to the center axis (CL).