A TFT-LCD array substrate is the glass backplane that carries the switching circuit for every pixel in an LCD panel. It includes thin-film transistors, scan lines, data lines, insulating layers, active semiconductor islands, passivation, vias, and transparent pixel electrodes.
Key Takeaways
- The Array substrate is the electrical backplane of the TFT-LCD cell.
- Bottom-gate TFT structures are a mainstream choice in mature a-Si TFT-LCD manufacturing.
- The physical pixel matrix and the equivalent circuit describe the same backplane from layout and electrical perspectives.
| Key definition: The TFT-LCD array substrate is the lower glass substrate of the LCD cell where the transistor matrix is fabricated. Its job is to select pixels row by row, write data voltage through the data lines, and hold the pixel state until the next refresh cycle. |
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Where the Array Substrate Fits in TFT-LCD Manufacturing
Front-end TFT-LCD cell manufacturing is commonly divided into three stages: Array, color filter, and cell assembly. The Array stage builds the TFT glass substrate; the color filter stage builds the CF glass; and cell assembly bonds the two substrates with liquid crystal between them.
Top-Gate vs Bottom-Gate TFT Structures
A TFT can be arranged as a top-gate or bottom-gate device. In a top-gate TFT, the gate electrode is above the semiconductor channel. In a bottom-gate TFT, the gate electrode is below the semiconductor channel. In mainstream a-Si TFT-LCD panels, bottom-gate TFTs are commonly used because they support mature large-area fabrication and stable backplane performance.
Main Layers in a Mainstream 6-Mask IPS Structure
A typical 6-mask IPS TFT stack includes the glass substrate, Gate electrode, Gate insulator, active layer, Source and Drain electrodes, passivation layer, pixel ITO electrode, and common ITO electrode. The active layer contains the a-Si semiconductor and the N+ a-Si ohmic contact layer.
Pixel Matrix and Equivalent Circuit
Across the full glass panel, the local TFT cross-section becomes a matrix of repeated pixel circuits. The scan line selects a row, the data line writes a voltage, and the TFT controls whether that signal reaches the pixel electrode. In practical pixel circuits, a storage capacitor is commonly paired with the TFT to help hold pixel voltage between refresh cycles.
Where to Go Next
After understanding the array substrate structure, continue with the 5-mask process flow and photolithography guide to see how these layers are fabricated step by step.
Frequently Asked Questions
What is a TFT-LCD array substrate?
It is the glass backplane that carries the TFT switching matrix, scan lines, data lines, insulating layers, active semiconductor, and transparent pixel electrodes used to control LCD pixels.
Why are bottom-gate TFTs common in TFT-LCD panels?
Bottom-gate TFTs fit mature large-area glass processing and are widely used in a-Si TFT-LCD manufacturing, especially for conventional LCD backplane flows.
What does the TFT backplane do?
The TFT backplane selects pixels, transfers data voltage, and helps hold the pixel state until the next refresh cycle.
Technical References
The following industry references support the material properties, TFT backplane terminology, and process context used in this guide.
- Applied Materials: Amorphous Silicon
a-Si has long been a dominant active-matrix TFT-LCD semiconductor; its low mobility explains why oxide and LTPS are used for higher-performance backplanes. - AGC: Glass Substrates for TFTs (AN100)
TFT-LCD glass must be alkali-free, heat resistant, chemically stable, and dimensionally stable during array fabrication. - Nippon Electric Glass: Alkali-Free Glass Substrate OA-11
Alkali-free display glass uses very low alkaline oxide content and supports dimensional stability through TFT process temperatures. - SID / Wiley: Beyond Amorphous-Silicon TFTs
a-Si mobility is limited compared with newer high-mobility TFT materials, which helps explain material trade-offs in LCD backplane design.
Related Deep-Dive Guides
- Main TFT-LCD Array process guide
- 5-mask TFT-LCD Array process flow
- TFT-LCD Array photolithography
- TFT-LCD Array materials
- Copper vs aluminum Gate electrodes
Related SuccessLCD Resources
For module sourcing, translate these Array-level requirements into a practical TFT LCD module RFQ checklist before confirming size, interface, brightness, touch, operating environment, and lifecycle targets.
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