[DISPLAY 101] #21 Etching


#21 Etching

Etching: The process of using a liquid solution to remove unwanted areas of a substrate and create a circuit pattern when manufacturing thin-film transistors.

After the process of patterning and developing, the next step is etching. This process involves using an etchant to remove the non-circuit material on the thin-film-transistor (TFT) substrate. After the photolithography and developing process, the photoresist component remains on the portion of the TFT substrate that corresponds to the pattern on the photomask. This serves to protect the circuit material beneath that location during the etching process. The final circuit is completed when the remaining photoresist component on the pattern is removed. The etching process can be seen as the step that creates the circuit pattern based on the photomask.

A diagram of the etching process

There are two types of etching: wet and dry. Wet etching involves using a solution to create a chemical reaction, while dry etching uses a reactive gas. Dry etching involves placing the substrate in a vacuum chamber, injecting etching gas, and then supplying electrical energy. This creates a plasma state, giving the ions of the ionized gas high kinetic energy. Accelerated by the electrode, the gas breaks the bonds of the circuit material and performs the etching. Dry etching is mostly used for high-resolution displays based on TFT substrates.

 Wet etchingDry etching
MethodChemical reaction using a solutionPhysical and chemical reaction using a gas
AdvantagesLow cost Fast process time Simplified processHigh accuracy Enables fine pattern formation
DisadvantagesLow accuracy Possible contamination of chemical substancesHigh cost Slow Complicated

Wet etching has the advantage of being relatively simpler and cheaper than dry etching but lower accuracy. There is the possibility of TFT contamination due to chemical substances in wet etching, but dry etching can selectively etch only the desired part, making it possible to implement very fine circuit patterns. After the etching process, the TFT substrate undergoes a photoresist stripping process.

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