Oxide Thin-Film Transistor Insulating Stack for Oxygen Retention

The insulating oxide layer is divided into multiple sub-layers (first insulating oxide layer, second insulating oxide layer, and third insulating oxide layer) with different densities and compositions. Each layer serves a specific function: the first layer provides oxygen replenishment, the second layer acts as a barrier to prevent hydrogen entry, and the third layer provides additional oxygen supply. This segmentation resolves the contradiction by achieving both process simplicity and reliability through a systematic multi-layer approach.

The patent employs a composite insulating oxide structure where layers with different materials and densities are combined. The first insulating oxide layer has lower density for oxygen release, the second insulating oxide layer has higher density for hydrogen barrier function, and the third insulating oxide layer provides additional oxygen supply. This composite structure simultaneously achieves fabrication simplicity and operational reliability.

The insulating oxide layers are formed with specific oxygen-rich compositions before the high temperature processes. The first and third insulating oxide layers are designed to release oxygen during subsequent high temperature annealing or deposition processes, thereby preventing oxygen loss from the semiconductor layer and maintaining its semiconductor characteristics while allowing mobility enhancement.

The insulating oxide layers act as oxygen sources that actively supply oxygen to the semiconductor layer during high temperature processes. The chemical composition of these layers (with excess oxygen) enables them to function as strong oxidizing agents, preventing reduction of the semiconductor layer and maintaining stoichiometry even under high temperature conditions that would otherwise cause oxygen loss and conductorization.