Stress-Generating Cellular Structure for Substrate Cleavage
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Solution Overview
Problem
Current methods for detaching thick layers from substrates in the semiconductor industry face challenges such as contamination risks, limited thermal expansion coefficient options, and high temperature requirements, which are unfavorable for achieving efficient cleavage.
Innovation Solution
A process involving the formation of a stress-generating structure with cellular walls composed of materials having different thermal expansion coefficients, applied locally to the substrate surface, which expands or contracts under heat treatment to generate stresses for cleavage, allowing for controlled detachment of layers between 1 and 100 micrometers without contaminating the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a metal layer is deposited on the substrate surface to generate thermal stress for cleavage, then the cleavage stress can be generated at the desired depth, but the substrate material risks contamination which is detrimental to device operation
Solution Approach 1:
The patent introduces an intermediate protective layer between the metal stress-generating layer and the substrate. This protective layer prevents direct contact and contamination of the substrate by the metal layer while still allowing the thermal stress to be transmitted through to generate cleavage at the desired depth. The protective layer acts as a mediator that enables the stress-generating function while blocking the harmful contamination effect.
2Productivity
If the thermal expansion coefficient of the stress-generating layer is changed to optimize cleavage, then the cleavage efficiency can be improved, but the material selection is limited to available materials on the market
Solution Approach 1:
The patent employs composite material structures, specifically combining metal layers with ceramic layers or polymer layers to create stress-generating layers with tailored thermal expansion coefficients. By adjusting the composition, thickness, and arrangement of these composite layers, the effective thermal expansion coefficient can be precisely controlled to match the requirements for optimal cleavage efficiency, overcoming the limitations of single-material selection.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the thermal expansion coefficient of the stress-generating layer through material composition variations. By changing the ratio of metals with different thermal expansion coefficients or selecting specific ceramic and polymer materials, the effective thermal expansion coefficient can be tuned to achieve the desired cleavage effect at lower temperatures while maintaining high cleavage efficiency.
3Force
If the substrate is heated to high temperature (around 800°C) to expand the stress-generating layer, then the cleavage can be achieved, but the substrate exhibits ductile nature which is unfavorable for obtaining cleavage
Solution Approach 1:
The patent changes the temperature parameter by using composite stress-generating layers with high thermal expansion coefficients that can generate sufficient thermal stress at lower temperatures (below 800°C). This temperature reduction is critical because it keeps the substrate in its brittle regime rather than transitioning to ductile behavior, thereby enabling successful cleavage. The parameter change involves both temperature reduction and material composition optimization.
Solution Approach 2:
The patent exploits thermal expansion by designing composite stress-generating layers with strategically selected materials that have significantly different thermal expansion coefficients. When heated to moderate temperatures, these layers expand differentially, generating strong thermal stresses that are sufficient to induce cleavage in the substrate without requiring high temperatures that would cause ductile behavior. The thermal expansion effect is amplified through the composite structure design.
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 enables efficient detachment of layers with greater freedom in choosing thermal expansion coefficients, reduces the necessary temperature for cleavage, and minimizes contamination risks, facilitating the use of the detached layers in semiconductor devices.
Implementation Method 1
said stress-generating structure being a cellular structure whose cell walls are perpendicular to the surface of the substrate and are composed of at least two materials having different coefficients of thermal expansion arranged to allow deformation of said walls under the effect of a heat treatment
Implementation Method 2
the application to said structure of a heat treatment adapted to cause the expansion or contraction of said structure so as to generate in the substrate a plurality of local stresses
Data Source
Figure 1~2
Figure 3~4B
Figure 4C~4E
AI summary
The invention relates to a method for cleaving a substrate (1) in order to detach a layer (1'), comprising: (i) the formation of a cellular structure (2) said to be stress-generating, locally attached to the surface of the substrate (1), the walls (2") of the cells (2') of which are perpendicular to the surface of the substrate and are composed of at least two materials (2a, 2b) having different coefficients of thermal expansion arranged to allow deformation of said walls under the effect of a heat treatment, allowing contraction or expansion of said structure in a plane parallel to the surface, (ii) the application of a suitable heat treatment to cause expansion or contraction of said structure (2), generating in the substrate (1) local stresses which generate a stress greater than the mechanical resistance of the substrate in a cleavage plane (C) defining the layer (1') to be detached.