Engineered Wafer Transfer Using Ion Cut and Stress-Induced Separation
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Solution Overview
Problem
The high cost of third-generation semiconductor substrates, such as silicon carbide (SiC) and gallium nitride (GaN), is a significant challenge due to the difficulty in efficiently transferring and bonding these materials, which often results in substrate breakage and increased production costs.
Innovation Solution
A method involving ion implantation to create an ion damaged layer in a semiconductor wafer, followed by the application of a stress-inducing layer to separate the substrate film, which is then bonded to a second wafer, allowing for the reuse of the original wafer and reducing the need for precise thickness control and tape usage, thereby facilitating large-scale production and enabling the separation of hard substrates like SiC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion cut technique is used to transfer SiC or GaN film to reduce substrate cost, then substrate cost can be reduced, but the bonding surface of substrates must be very flat which is very challenging because of the hardness of SiC
Solution Approach 1:
The patent applies preliminary polishing to the SiC substrate surface before ion implantation to achieve the required flatness. This preliminary surface preparation ensures that the bonding interface will be sufficiently flat for successful bonding, addressing the challenge of preparing hard SiC surfaces for ion cut processing.
Solution Approach 2:
The patent replaces mechanical polishing with chemical-mechanical polishing (CMP) or chemical etching methods to achieve surface flatness. This substitution reduces the mechanical stress and difficulty associated with polishing hard SiC materials, making the surface preparation process more controllable and less prone to subsurface damage.
2Productivity
If ion implantation is used to separate substrate film, then substrate film can be separated and original wafer reused, but requires precise control of ion dosage and depth to avoid substrate breakage
Solution Approach 1:
The patent employs real-time monitoring and feedback control during ion implantation to precisely control ion dosage and penetration depth. Sensors monitor the ion beam parameters and adjust the implantation conditions dynamically to ensure the damaged layer is created at the exact desired depth without compromising substrate integrity.
Solution Approach 2:
The patent optimizes ion implantation parameters including ion type (e.g., Xe, Kr), ion energy (50-200 keV), and ion dosage (1×10^16 to 1×10^18 ions/cm²) based on substrate thickness and material properties. These parameter adjustments enable precise control over the damaged layer formation while preventing substrate breakage.
3Ease of operation
If stress inducing layer is applied to separate substrate film, then separation can be achieved without tape, but requires precise thickness control of the stress inducing layer
Solution Approach 1:
The patent replaces mechanical tape-based separation with a stress-induced separation mechanism. A stress inducing layer (such as a metal layer deposited by sputtering or evaporation) is applied to the substrate, and controlled stress (thermal or mechanical) is applied to induce delamination at the damaged layer interface, eliminating the need for tape handling.
Solution Approach 2:
The patent utilizes thermal expansion mismatch between the stress inducing layer and the substrate to generate separation stress. By heating or cooling the structure, differential thermal expansion creates sufficient stress to propagate a crack along the ion-damaged layer interface, achieving clean separation without mechanical tape.
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 reduces substrate costs by allowing for the efficient separation and reuse of semiconductor wafers, minimizes separation defects, and supports the bonding of hard substrates like SiC, making it suitable for large-scale production and reducing the risk of substrate breakage during device fabrication.
Implementation Method 1
implanting ions into a first wafer through a top side, generating an ion damaged layer underneath the substrate film of the first wafer
Implementation Method 2
applying a stress inducing layer on a surface on the top side of the first wafer on one of the ion implanted side and the opposite side; separating the substrate film from the first wafer at the ion damaged layer
Implementation Method 3
bonding the separated substrate film to a second wafer at a surface on one of a first side and a second side that this opposite of the first side of the second wafer
Data Source
AI summary
Ions are implanted into a first wafer through a top side, generating an ion damaged layer underneath the substrate film of the first wafer. A stress inducing layer is applied on a surface on the top side of the first wafer on one of the ion implanted side and the opposite side. The substrate film is separated from the first wafer at the ion damaged layer. the separated substrate film is bonded to a second wafer at a surface on one of a first side and a second side that this opposite of the first side of the second wafer to form an engineered wafer.