Abstract
Subsurface damage of 4H-silicon carbide (SiC) wafers, which is detrimental to the performance and lifetime of SiC-based photoelectric devices, is easily induced during surface machining process due to their particular mechanical and physical properties. A nondestructive and effective characterization technique is essential for high quality products in the wafer manufacturing process. A method based on the Mueller Matrix Spectroscopic Ellipsometry (MMSE) is proposed to detect the nanoscale subsurface damage of 4H-SiC wafers induced by grinding and polishing. The Mueller matrix elements which are sensitive to the damage information have been identified through both simulation and experiment. The damage layer and its roughness are considered in optical modeling at different processing stages. The results show that both the surface texture and the damage layer contribute to the Mueller matrix values. The fitting thickness of the damage layer is consistent with the value from transmission electron microscope (TEM); the refractive index of the damage layer matches the surface elements analysis result from X-ray photoelectron spectroscopy (XPS). The results suggest that the MMSE-based method could offer a promising nondestructive method to detect global wafer subsurface damage and its evolution during grinding and polishing, which eventually could benefit process optimization in the whole wafer manufacturing process.
Highlights
4H-silicon carbide (SiC) is considered as one of the most promising third-generation semiconductor materials with applications in many cutting-edge fields, such as semiconductor electronics, optics, and graphene growth [1, 2]
A nondestructive detection method based on Mueller matrix spectroscopic ellipsometry is proposed to evaluate the subsurface damage of 4H-SiC wafers in rough grinding, fine grinding, and chemical mechanical polishing (CMP) stages
When the surface texture direction is perpendicular to the incident plane, the Mueller matrix can obtain maximum response from the damage and interface
Summary
4H-silicon carbide (SiC) is considered as one of the most promising third-generation semiconductor materials with applications in many cutting-edge fields, such as semiconductor electronics, optics, and graphene growth [1, 2]. SiC Damage Studied by Ellipsometry substrate processing [6], which will impair the mechanical, electronic, and optical properties of materials [7] For this reason, the characterization of subsurface damage is conducive to advanced applications. The processing flow of SiC substrate mainly includes rough grinding, fine grinding, and chemical mechanical polishing (CMP) [7, 8]. The nondestructive methods include micro-Raman spectroscopy, optical coherent tomography, photoluminescence, and laser scattering method Their detection accuracy or efficiency is limited, or inappropriate for accurately measuring the thickness of the very thin damage layer. The damage layers induced by rough grinding, fine grinding, and CMP 4H-SiC off-axis cut wafers are characterized by MMSE.
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