Femtosecond Laser SiC Wafer Separation With Thin Amorphous Layers

The patent replaces the mechanical diamond wire cutting system with a laser-based modification system. A laser beam is used to create a modified layer within the silicon carbide ingot that has reduced bonding strength, allowing the material to be separated without mechanical contact. This substitution eliminates the 150-300 micron kerf loss associated with mechanical cutting while maintaining high productivity through controlled laser processing.

The patent modifies the physical and chemical parameters of the silicon carbide material by creating an amorphous modified layer with different structural properties than the original crystalline material. By controlling laser parameters (wavelength, pulse duration, energy density) and processing conditions (gas atmosphere, temperature), the modified layer achieves specific properties including reduced bonding strength and controlled thickness, enabling separation with minimal material loss.

The patent employs pulsed laser operation instead of continuous laser exposure. By using periodic pulses with controlled duration, frequency, and energy, the modification process achieves precise thickness control. The pulsed nature allows heat diffusion control and prevents excessive energy accumulation that would lead to overly thick modified layers, while still achieving the desired amorphous transformation for easy separation.

The patent replaces conventional continuous laser modification with a controlled pulsed laser system that uses precise parameter management. By substituting the traditional approach with a pulsed regime and controlling atmospheric conditions (inert gas or vacuum environment), the system achieves thin modified layers (reducing kerf loss) while maintaining the amorphous structure necessary for easy separation.

The patent carefully controls multiple parameters including laser wavelength, pulse duration, energy density, and atmospheric conditions to achieve the optimal balance between modified layer thickness and bonding strength reduction. By adjusting these parameters, the system creates a modified layer that is thin enough to minimize kerf loss but sufficiently modified to achieve the desired bonding strength reduction for easy separation.

The patent utilizes the phase transition of silicon carbide from crystalline to amorphous state through controlled laser heating. This phase transition fundamentally changes the material's bonding characteristics, reducing bonding strength while allowing precise control of layer thickness through parameter optimization. The amorphous modified layer provides the necessary properties for easy separation with minimal material loss.