First of all, we know that the general process of photolithography is that a wafer (usually 300mm in diameter) is coated with a layer of photoresist, and then the light passes through a maskorreticle with a circuit pattern already engraved Irradiated onto the wafer, the photoresist portion on the wafer is photosensitive (corresponding to the patterned portion), and then the subsequent processing of dissolving the photoresist and etching the wafer is performed. Then apply another layer of photoresist and repeat the above steps dozens of times to achieve the required requirements.

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For simplified structure, please see the figure below. The mask plate and the wafer are each mounted on a motion platform (reticlestage and waferstage). During lithography, the two move to a specified position and the light source is turned on. After the light passes through the reticle, it passes through a lens, which can reduce the circuit pattern to a quarter, and then project it onto the wafer to make the photoresist partially sensitive.

There are many dies on a wafer, and each die is engraved with the same circuit pattern, that is, a wafer can produce many chips. The typical size of a die is 26 × 32mm.

There are two main types of lithography machine, one is called stepper, that is, after the mask and a certain die on the wafer are moved into place, the light source is turned on and off to complete a lithography, and then the wafer movement makes the next die in place, and then perform a photolithography, and so on.

Another kind of lithography machine is called scanner, that is, the light is limited to the area of ??a slit. During lithography, the mask and the wafer move at the same time, so that the light sweeps through the area of ?a die in a scanning manner, thus the circuit The pattern is engraved on the wafer.

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