Semiconductor Wafer Separation Using Thermal Stress Wave Timing

The patent replaces the mechanical wire saw slicing method with a laser-based separation method. A pulsed laser beam is applied to the semiconductor ingot to generate thermal stress waves that propagate through the material, causing separation layers to form at predetermined depths without mechanical contact. This substitution eliminates the material waste associated with wire saw slicing while maintaining efficient wafer production.

The patent utilizes changes in the optical and thermal parameters of the semiconductor ingot material. By controlling the laser pulse duration, wavelength, and intensity, thermal stress waves are generated that propagate through the ingot and create separation layers at specific depths. The timing of subsequent laser pulses is synchronized with the thermal stress wave propagation to form fracture layers precisely where needed, enabling controlled wafer separation without wasting material.

The patent establishes the upper surface of the semiconductor ingot as a reference plane before the laser separation process begins. By pre-defining this reference surface and using it as the basis for timing the laser pulse application, the system eliminates the need for repeated surface height detections during production. The timing of laser pulses is calculated based on the known reference surface position and the expected propagation speed of thermal stress waves through the material.

The patent makes the semiconductor ingot itself serve as the reference for timing and positioning. The known physical properties of the material (such as thermal stress wave propagation speed) and the pre-established reference surface allow the system to automatically determine when and where to apply laser pulses without requiring external measurement devices during the production process. The material's own characteristics are used to guide the separation process.