LTPS TFT Substrate Grain Control via Silicon Oxide Photomask

The patent applies local quality by depositing a silicon oxide layer selectively in the display area to create different crystallization conditions in different regions. The silicon oxide layer modifies the laser annealing effect locally, resulting in smaller, more uniform grains in the display area while the drive area develops larger grains for higher electron mobility, thus resolving the contradiction between uniformity and electron mobility across different areas.

The silicon oxide layer serves as an intermediary material that mediates the laser annealing process. It absorbs and modulates the laser energy, creating the desired crystallization effect in the drive area without requiring complex process equipment or multiple processing steps. This intermediary approach achieves high electron mobility through a relatively simple additional deposition and annealing sequence.

The patent segments the substrate into two distinct functional areas with different grain structures: the display area with small, uniform grains for electrical uniformity, and the drive area with large grains for high electron mobility. This segmentation is achieved through selective silicon oxide layer deposition and laser annealing, allowing each area to be optimized for its specific function without compromising the other.