SiC Wafer Thinning by Laser Interface Separation
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Solution Overview
Problem
The high cost and low yield of silicon carbide (SiC) power devices due to the inefficiency of thinning processes, which result in significant material waste and substrate damage, limiting their application in various fields.
Innovation Solution
A method involving temporary bonding of a substrate carrier to a SiC wafer and performing laser irradiation to separate the SiC layers, allowing for efficient thinning and reuse of the debonded layers, reducing material waste and preparation costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional mechanical grinding is used to thin the SiC substrate, then the substrate thickness is reduced, but material waste is severe and the risk of substrate rupture is high
Solution Approach 1:
The patent replaces conventional mechanical grinding with laser irradiation technology. The laser beam is focused at the interface between the SiC substrate and dielectric layer to achieve precise separation and thinning without mechanical contact, thereby eliminating mechanical wear, reducing material waste, and preventing substrate rupture caused by mechanical stress.
Solution Approach 2:
The patent utilizes the optical parameters of the materials involved. By selecting a laser wavelength where the SiC substrate has low absorption and the dielectric layer has high absorption, the laser energy is selectively absorbed at the interface, enabling precise thermal separation and thinning with minimal material removal and waste.
2Length of stationary object
If conventional mechanical grinding is used to thin the SiC substrate, then the substrate thickness is reduced, but the risk of substrate rupture increases
Solution Approach 1:
The patent replaces mechanical grinding with laser irradiation, eliminating mechanical contact and associated stresses that cause substrate rupture. The laser-induced thermal separation occurs without mechanical force, maintaining substrate integrity while achieving the desired thickness reduction.
Solution Approach 2:
By controlling laser parameters (wavelength, power, pulse duration) and utilizing the optical property differences between SiC and dielectric materials, the patent achieves selective heating and separation at the interface without excessive thermal diffusion that could cause substrate damage or rupture.
3Reliability
If a thick SiC substrate is used to reduce damage risk, then substrate reliability improves, but preparation costs increase due to excessive material usage
Solution Approach 1:
The patent uses laser irradiation to achieve precise, contactless separation and thinning of the substrate. This allows the use of thicker initial substrates for reliability without incurring excessive material waste, as the laser process can precisely remove only the necessary amount of material with minimal waste and no mechanical damage.
Solution Approach 2:
The patent exploits the differential optical absorption coefficients of SiC and dielectric materials at specific laser wavelengths. This enables selective heating and separation at the interface, allowing precise control over material removal while maintaining substrate integrity, thus reducing waste even when starting with thicker substrates.
4Productivity
If laser irradiation is performed with high energy to improve ablation efficiency, then thinning speed increases, but the risk of damaging the first silicon carbide layer increases
Solution Approach 1:
The patent employs local heating through focused laser irradiation at the interface between the SiC substrate and dielectric layer. By concentrating energy precisely at the separation interface rather than uniformly heating the entire substrate, the patent achieves efficient separation and thinning while protecting the first silicon carbide layer from thermal damage.
Solution Approach 2:
The patent utilizes the optical property differences between materials: the SiC substrate has low laser absorption while the dielectric layer has high absorption. This enables selective heating at the interface with appropriate laser wavelength selection, achieving high ablation efficiency for the dielectric layer while minimizing energy absorption and potential damage to the SiC layers.
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 reduces the preparation costs of SiC power devices by minimizing material waste and substrate damage, improving the thinning process efficiency and compatibility with high-temperature semiconductor processes.
Implementation Method 1
performing laser irradiation on the wafer from the first side, so that energy of a laser is focused for ablation at an interface between the second silicon carbide layer and the dielectric layer
Implementation Method 2
a refractive index of the dielectric layer is different from that of the second silicon carbide layer. Therefore, after the laser is irradiated into the wafer from a surface that is of the second silicon carbide layer and that is away from the first silicon carbide layer, the laser is easily focused and absorbed at the interface between the dielectric layer and the second silicon carbide layer
Implementation Method 3
temporarily bonding a temporary substrate carrier to the wafer on the second side
Data Source
AI summary
A method for thinning a wafer is provided which is related to the field of semiconductor technologies, to resolve problems of a low yield, a complex process, and high preparation costs of a SiC power device. The wafer which may alternatively be understood as a composite substrate, includes a first silicon carbide layer, a dielectric layer, and a second silicon carbide layer that are disposed in a stacked manner. The wafer has a first side and a second side that are opposite to each other, and a side that is of the second silicon carbide layer and that is away from the first silicon carbide layer is the first side of the wafer.