Major Subassemblies
A typical stepper has the following subassemblies: wafer loader, wafer stage, wafer alignment system, reticle loader, reticle stage, reticle alignment system, reduction lens, and illumination system. Process programs for each layer printed on the wafer are executed by a control system centering on a computer that stores the process program, reads it, and communicates with the various subassemblies of the stepper in carrying out the program's instructions. The components of the stepper are contained in a sealed chamber that is maintained at a precise temperature to prevent distortions in the printed patterns that might be caused by expansion or contraction of the wafer due to temperature variations. The chamber also contains other systems that support the process, such as air conditioning, power supplies, control boards for the various electrical components, and others.
Read more about this topic: Stepper
Famous quotes containing the word major:
“A major misunderstanding of child rearing has been the idea that meeting a child’s needs is an end in itself, for the purpose of the child’s mental health. Mothers have not understood that this is but one step in social development, the goal of which is to help a child begin to consider others. As a result, they often have not considered their children but have instead allowed their children’s reality to take precedence, out of a fear of damaging them emotionally.”
—Elaine Heffner (20th century)