Laser-Assisted Wafering of 4H-SiC: From Subsurface Modification and Crack Coalescence to Controlled Separation

Laser-assisted wafering can reduce material consumption in silicon carbide (SiC) substrate manufacturing, but successful subsurface modification does not, by itself, guarantee controlled wafer release. This review treats 4H-SiC wafering as a two-step process comprising laser formation of a weakened subsurface layer, followed by assisted separation. We connect nonlinear energy deposition, phase transformation and residual stress to crack nucleation, interaction and coalescence, and then assess mechanical and ultrasonic separation, polymer-assisted cold splitting, continuous-wave laser splitting, other thermal-stress routes, and chemical or hybrid release within a common fracture-mechanics framework. Reported results show that crystallographic orientation, scan arrangement, crack coplanarity, acoustic coupling and liquid medium strongly affect separation. Nominal separation stress, residual stripping force and internally generated thermal stress are distinct metrics and should not be compared directly. Reported separation strengths span more than three orders of magnitude, from above 38 MPa to about 0.04 MPa, primarily because laser processing produces very different crack-network connectivity. As-split roughness ranges from about 0.16 to 6.5 µm and is governed mainly by the laser step and 4° off-cut geometry. Joint optimization of modification and separation, together with standardized reporting, is therefore essential for scalable low-loss wafering.