Can someone explain how photolithography works in VLSI?

We use photolithography to precisely transfer designs onto a wafer. I find it interesting that a photoresist is used to make the wafer sensitive to light, and then a photomask projects the design onto it. In the next step, we develop the wafer, which means we wash away either the exposed or unexposed areas of the photoresist, depending on the type used. For some steps, the remaining photoresist acts as a mask directly, but sometimes we need an additional layer underneath that takes over the masking job. This technique is essential for ensuring that each layer of the chip is correctly patterned.

You’ll notice that photolithography involves several steps to get the desired patterns onto a wafer. First, a photoresist is applied to the wafer, usually by spinning it to get an even coat. Then, light through a photomask creates a pattern on the photoresist. Depending on whether you’re using positive or negative photoresist, the exposed areas will either become more soluble or less soluble. After developing, the pattern is either left as is or used to create a mask for further processing. This process is key to making sure that the chip’s layers are built accurately and consistently.