Semiconductor Wafer Peeling with Controlled Crack Initiation
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Solution Overview
Problem
Existing wafer manufacturing methods face issues with sagging or chipping during grinding and polishing processes, leading to stress concentration at unintended locations, which can cause cracks and lower material yield.
Innovation Solution
A method involving a peeling process that applies tensile stress to a semiconductor ingot with a pre-formed peeling layer, creating a stress-concentrated region inside the outer peripheral edge to initiate crack propagation from a controlled starting point, using a peeling jig to separate the wafer from the ingot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding and polishing processes are used to manufacture semiconductor wafers, then wafer separation can be achieved, but sagging or chipping occurs at the outer peripheral edge leading to stress concentration and unintended cracks
Solution Approach 1:
The patent applies preliminary action by forming a modified layer and initiating cracks at a predetermined position inside the outer peripheral edge before the actual wafer separation process. This pre-positioned crack initiation point ensures that subsequent separation forces propagate cracks along the intended path rather than causing unintended cracking at the outer peripheral edge during grinding and polishing.
Solution Approach 2:
The patent introduces an intermediary modified layer created by laser irradiation between the applied stress and the crystal structure. This modified layer acts as a mediator that concentrates stress at a controlled location inside the outer peripheral edge, directing crack propagation along the c-surface through the peeling layer rather than causing uncontrolled cracking at the outer peripheral edge during mechanical processing.
2Manufacturing precision
If laser beam irradiation is applied to form a modified layer, then crack propagation can be controlled along the c-surface, but the process complexity increases
Solution Approach 1:
The patent extracts the crack initiation function from the mechanical grinding and polishing process and transfers it to a laser-based modified layer formation process. By separating these functions, the laser process specifically creates the modified layer and initiates cracks at the precise location inside the outer peripheral edge, while the subsequent mechanical process simply propagates these pre-initiated cracks along the controlled path through the peeling layer.
3Productivity
If external force is applied for wafer separation, then separation efficiency is improved, but unintended cracks may occur at stress-concentrated locations
Solution Approach 1:
The patent applies local quality by creating a non-uniform stress distribution through the modified layer, concentrating stress at a specific location inside the outer peripheral edge rather than distributing it uniformly. This localized stress concentration ensures that cracks initiate and propagate only through the intended peeling layer path, preventing unintended cracking at other locations while maintaining high separation efficiency with applied external force.
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
Stabilizes the peeling process, reducing the risk of unintended cracks and improving material yield by controlling the initiation of crack propagation from a predetermined stress-concentrated region.
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
a converging point of a laser beam having a wavelength to which the ingot, fixed on the supporting table, has transparency
Implementation Method 3
forming, with an application of the tensile stress to the peeling object, a stress-concentrated region in the peeling layer
Implementation Method 4
propagating cracks from the stress-concentrated region as a starting point, thereby peeling between a first side portion and a second side portion
Data Source
AI summary
A method for manufacturing a semiconductor wafer includes steps of: preparing a peeling object including a single crystal body of a semiconductor having a pair of major surfaces composed of front and back surfaces, the peeling object having a peeling layer provided along at least one of the major surfaces; applying a tensile stress to the peeling object 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 positioned inside an outer peripheral edge in a radial direction of which the center is a center axis 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 having the peeling layer interposed therebetween in a direction parallel to the center axis.