DISPLAY 101
#19 Exposure
| Exposure: The process of exposing a photoresist to light through a photomask so that chemical changes are induced in the photoresist in a pattern that matches the photomask. |
Let’s take a look at exposure, a key process in photolithography for making TFTs. Exposure is the concept of shining light onto matter. It’s a principle that’s also used in film cameras. When film that reacts to light is put inside a camera, and the shutter is opened to expose that film to outside light, a chemical change occurs in the film to create an image. The TFT process is similar, in that a circuit pattern is created on a substrate after being exposed to light.
Make a fine electronic circuit pattern with light
Photolithography plays an important role in increasing the definition of displays by creating fine-grained circuit patterns on thin-film transistors (TFTs), a key semiconductor device that regulates the pixel brightness of displays.
An essential step in this important process is exposure to light. When light passes through a photomask with a circuit pattern, the light shines through it in that specific circuit pattern and the photoresist is exposed to the light in that pattern as well. The photoresist is then altered by the light in the specific circuit pattern, so that the pattern can be etched onto the substrate in a later step.
Because the circuit patterns that are engraved onto the display TFTs can include details that are measured in micrometers, it is necessary to use ultraviolet light because of its shorter, more precise wavelength.
After the exposure process, the photolithography is completed in the development, etching, and stripping processes.
