SiC Wafer Residual Stress Balancing to Prevent Warpage

The patent segments the wafer thinning process into multiple controlled stages with intermediate annealing treatments. Instead of thinning to the final thickness in one step, the wafer is thinned incrementally with stress-relief annealing performed at intermediate thicknesses, thereby managing residual stress accumulation and preventing wafer breakage while achieving the target thin thickness for high-speed device performance.

The patent changes the physical-chemical parameters of the wafer through controlled annealing treatments at specific temperatures (e.g., 1000-1500°C) in nitrogen or oxygen atmospheres. These parameter changes (temperature, atmosphere, time) modify the stress state and microstructure of the thinned wafer, relieving residual stress and preventing bending while maintaining the thin thickness required for high device speed and low parasitic capacitance.

The patent applies preliminary stress-relief annealing treatments before completing the full thinning process. By performing annealing at intermediate stages while the wafer still has sufficient thickness to withstand handling, the wafer's stress state is preemptively managed, preventing stress concentration and breaking during subsequent thinning steps or device fabrication processes.

The patent introduces intermediate annealing steps that act as a cushioning mechanism against stress accumulation. These annealing treatments create a buffer by periodically relieving residual stress during the thinning process, preventing the build-up of critical stress levels that would lead to wafer breaking, thereby ensuring wafer reliability throughout the manufacturing process.

The patent implements periodic annealing treatments at regular intervals during the thinning process. This periodic action creates a standardized, repeatable manufacturing sequence (thin-anneal-thin-anneal) that, while adding steps, provides systematic stress control. The periodic nature makes the process more manageable and controllable compared to attempting to manage stress in a continuous or ad-hoc manner during thinning.

The patent integrates stress-relief annealing as continuous useful actions within the thinning process rather than separate corrective measures. By embedding annealing steps within the thinning sequence, the process continuously manages stress accumulation rather than allowing it to build up and then correcting it later, thereby reducing overall manufacturing complexity despite the additional thermal processing steps.