Mask aligner is used to:
I. Alignment of wafer to mask
II. Coat photoresist on wafer
III. Expose the coated wafer
IV. Developing the pattern, printed on wafer
I, II
II, III
I, III
III, IV
A mask aligner is a device used in semiconductor manufacturing to create the desired patterns on a wafer. It involves several steps:
I. Alignment of wafer to mask: The first step is to align the wafer with the photomask, which contains the desired pattern. The mask aligner ensures accurate alignment of the wafer and the mask.
II. Coat photoresist on wafer: After alignment, a thin layer of photoresist is coated onto the surface of the wafer. The photoresist is a light-sensitive material that will be used to transfer the pattern from the mask to the wafer.
III. Expose the coated wafer: Once the photoresist is evenly coated on the wafer, the mask aligner exposes the wafer to a specific pattern of light. This pattern of light passes through the mask and gets transferred onto the photoresist layer.
IV. Developing the pattern printed on the wafer: After exposure, the coated wafer is developed. This step involves removing the unexposed photoresist using a chemical solution, leaving behind the desired pattern on the wafer.
So, the correct answer would be: I, III. The mask aligner is used for aligning the wafer to the mask (I) and exposing the coated wafer to the desired pattern of light (III). The coating of photoresist on the wafer (II) and development of the pattern (IV) are typically done using other equipment or processes.