SEM, AFM and TEM Studies for Repeated Irradiation Effect of Femtosecond Laser on 4H-SiC Surface Morphology at Near Threshold Fluence

Abstract

In order to investigate the interaction of femtosecond (fs) laser and hard-to-process semiconductor material 4H-SiC at near-threshold fluence, fs laser was repeatedly irradiated to SiC surface at different scanning velocities and scan times. The evolutions of surface morphologies were observed and discussed according to Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Transmission Electron Microscope (TEM). Discontinuous zones were ablated in SiC surface after laser irradiation at nearthreshold fluence 1.1 J/cm 2 . High spatial frequency rippled structures substantially shorter than the wavelength of incident fs laser were fabricated. The width of the ablated zones increased with lower scanning velocities and more scan times. The mechanism was discussed. Incubation effect occurred in the subsurface of SiC triggered inhomogeneous energy deposition accumulation, which was responsible for the discontinuous ablated zones. Moreover, an amorphous layer with a thickness of about 30 nm was observed in 4H-SiC surface where no ablation was induced after repeated irradiation. This was discussed and explained from the aspects of molecular dynamics simulations of fs laser irradiation to semiconductor materials.

Investigation on the Processing Quality of Nanosecond Laser Stealth Dicing for 4H-SiC Wafer

“…Silicon carbide (SiC), due to its high mechanical performance and excellent electrical properties, 1 is suitable for semiconductor devices. It is characterized by a wide band gap, high breakdown electric field, high thermal conductivity and high electron saturation rate compared to Si.…”

Effect of Mn-Based Slurries on Chemical Mechanical Polishing of SiC Substrates

“…12,13 Wang et al used femtosecond-laser-irradiationassisted CMP to improve material removal by destabilizing surface crystals. 14 Yuan et al used UV-TiO 2 -photocatalysis-assisted CMP to increase the material removal rate and surface quality of 4H-SiC wafers. [15][16][17] These studies demonstrate that CMP can increase the material removal rate for SiC substrates by promoting interfacial chemical reactions.…”

Effect of Using High-Pressure Gas Atmosphere with UV Photocatalysis on the CMP Characteristics of a 4H-SiC Substrate

“…SiC semiconductors are widely applicable as key components in industrial fields, such as lighting, communications, and transportation. [3][4][5][6] However, in addition to its extremely stable physical chemical properties, SiC has a hardness that is second only to diamond (Vickers hardness of 2840 ∼ 3320 kg mm −2 ) and is therefore very difficult to process. In particular, problems, such as a low processing efficiency and residual surface scratches, are encountered in the chemical mechanical polishing (CMP) of SiC, which has extremely high surface flatness and surface roughness requirements.…”