Technology Computer-Aided Design-Based Simulation Program with Integrated Circuit Emphasis Model for...

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Device Physics

Background:

• The back-channel-etched (BCE) process is attractive for mass-producing thin-film transistors (TFTs) due to reduced mask steps.
• Realizing long channels in BCE TFTs necessitates the use of floating metals, acting as bridges within the semiconductor layer.

Purpose of the Study:

• To investigate the characteristics of amorphous silicon (a-Si) TFTs with floating metals fabricated using the BCE process.
• To analyze the impact of active layer thickness and the number of floating metals on TFT performance and scaling.
• To develop a new SPICE model for TFTs incorporating floating metals.

Main Methods:

• Utilized Technology Computer-Aided Design (TCAD) simulations (Atlas 3D) to model TFT behavior.
• Compared simulation predictions with experimental measurements from fabricated TFTs.
• Analyzed the influence of active layer resistance and thickness on device scaling.

Main Results:

• TFTs with floating metals exhibit non-ideal scaling, particularly with thick and resistive active layers.
• A higher number of floating metals requires greater correction for ideal scaling.
• The channel influence under the floating metal is significant, estimated at 89% due to source-channel capacitance.

Conclusions:

• Floating metals in BCE TFTs present unique scaling challenges influenced by active layer properties.
• The developed SPICE model accurately represents TFTs with floating metals, aiding in circuit design.
• Optimizing active layer characteristics is crucial for achieving desired performance in long-channel BCE TFTs.