TFTsubstraat

TFT-substraat, or TFT backplane substrate, is the base material on which thin-film transistors (TFTs) are fabricated to form the active matrix backplane of flat-panel displays and other electronic devices. The substrate provides mechanical support, electrical insulation, and a smooth surface for sequential deposition of semiconductor, dielectric, and conductor layers.

Common rigid substrates are glass varieties such as soda-lime and borosilicate glass, typically 0.5–1.1 mm thick. Flexible TFTs use polymer substrates such as polyimide (PI), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN), typically tens to hundreds of micrometers thick. Substrates may include barrier and adhesion layers to prevent moisture and oxygen ingress and to ensure adhesion of metal and oxide films.

Most backplanes for LCDs use amorphous silicon (a-Si) TFTs on glass; higher-performance LTPS (polycrystalline silicon) and oxide semiconductors like IGZO are used for higher mobility, smaller pixel pitch, and low-voltage operation. A typical stack places the gate electrode on the substrate, followed by gate dielectric, the TFT active layer, source/drain contacts, and passivation or protection layers.

In flexible displays, low-temperature processing is essential; substrates must tolerate processing temperatures and provide compatible surface chemistry. The choice of substrate affects display performance, including contrast, response time, and power consumption, and drives issues such as thermal expansion mismatch and moisture barriers. The TFT-substrate is thus a key component in the manufacturing of LCDs, OLEDs, and other active-matrix displays.