TFT Copper Electrode Adhesion via Nitrogen Plasma Passivation
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Solution Overview
Problem
Copper electrodes in thin film transistors (TFTs) face electrical degradation and peeling issues due to reaction with silicon and poor adhesion, exacerbated by the use of oxygen-containing barrier layers which are damaged during PECVD processes, leading to bubble formation and reduced barrier effectiveness.
Innovation Solution
A manufacturing method involving the formation of a gate electrode, gate dielectric layer, semiconductor layer, source/drain electrodes with a barrier and conductive layer, and a passivation layer treated with nitrogen-containing plasma to prevent barrier layer reduction and damage, followed by a protection layer to isolate the electrodes from reactive gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxygen-containing compound (oxide or oxynitride) is used as a barrier layer, then copper silicide generation is avoided, but the barrier layer is reduced and damaged by reacting gas in PECVD process, producing bubbles and resulting in peeling of copper film
Solution Approach 1:
The patent applies preliminary action by forming a protective nitrogen-containing layer on the barrier layer surface before the PECVD process. This pre-protection measure prevents the oxygen-containing barrier layer from being reduced and damaged during subsequent PECVD processing, eliminating bubble formation and copper film peeling while maintaining barrier effectiveness against copper silicide generation.
2Reliability
If copper metal is used in source/drain electrodes, then low resistance and high melting point are achieved, but copper easily reacts with silicon to generate copper silicide and has high diffusion coefficient in dielectric layer, resulting in electrical degradation
Solution Approach 1:
The patent employs an intermediary approach by introducing a barrier layer composed of oxygen-containing compound (oxide or oxynitride) between the copper metal source/drain electrodes and the silicon-containing layers. This intermediate layer effectively prevents direct contact between copper and silicon, blocking copper silicide generation and copper diffusion into the dielectric layer, thereby maintaining electrode performance without harmful reactions.
3Reliability
If barrier layer is formed to prevent copper silicide generation, then copper-silicon reaction is avoided, but poor adhesion between copper metal and dielectric layer results in peeling
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of the barrier layer through nitrogen-containing plasma treatment or deposition of nitrogen-containing material. This changes the surface composition and chemical characteristics of the barrier layer, improving its adhesion to both the copper metal and the surrounding dielectric layers, thereby preventing peeling while maintaining its function as a barrier against copper silicide generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively prevents barrier layer reduction and damage, alleviates peeling of copper electrodes, and enhances the stability of the TFT structure by forming a passivation layer that isolates the source/drain electrodes from reactive gases, thereby improving the manufacturing process yield and electrode integrity.
Implementation Method 1
The source/drain electrodes are treated by nitrogen-containing plasma to form a passivation layer on a surface of the source/drain electrodes
Implementation Method 2
The passivation layer is disposed over the surface of the source/drain electrodes... the passivation layer that isolates the source/drain electrodes from reactive gases
Data Source
AI summary
A thin-film transistor (TFT) includes a gate electrode, a gate dielectric layer, a semiconductor layer, source/drain electrodes, a passivation layer and a protection layer. The gate electrode is disposed on a substrate. The gate dielectric layer covers the gate electrode and the substrate. The semiconductor layer is disposed on the gate dielectric layer and above the gate electrode. The semiconductor layer has a channel region disposed above the gate electrode and source/drain regions disposed at both sides of the channel region. The source/drain electrodes are disposed on the source/drain regions of the semiconductor layer and each has a barrier layer disposed on the source/drain regions of the semiconductor layer and a conductive layer disposed on the barrier layer. The passivation layer is disposed over the surface of the source/drain electrodes. The protection layer is disposed over the substrate, the passivation layer, and the channel region of the semiconductor layer.