Glossary

Aligner is pertaining to the type of semiconductor manufacturing equipment used to transfer patterns onto wafers through the use of photolithography and exposure. Aligners can "align" a new pattern on a reticle or mask to patterns already on the wafer, hence the name aligner. (see Step and Repeat, Step and Scan below)

There are four main types of aligners: contact, proximity, projection, and steppers, to wit:

1. Contact aligner - a process equipment utilized to align masks to wafers and transfer patterns to the wafers by photolithography. In a contact aligner the wafer is actually brought into contact with the wafer during exposure. The first contact aligner became commercially available in 1963.

2. Proximity aligner - an alignment system in which a mask and wafer are separated by a few microns in distance and the mask pattern is aligned and exposed onto the wafer.

3. Projection aligner - an alignment system in which a mask and wafer are separated by a significant distance and the mask pattern is focused onto the wafer, aligned and exposed. Projection printing was invented in 1973 and by the mid 1970s had largely replaced contact and proximity aligners.

4. Stepper - an aligner used to transfer a reticle pattern onto a wafer. With its limited field of view, low throughput, and high cost, such equipment is usually used only for features size smaller than 1.5?, where resolution and line-width control are critical.


Step and Repeat - a system that exposes a wafer by exposing an area of the wafer and then stepping to the next adjacent area of the wafer to perform the next exposure. The system steps and exposes repeatedly until the whole wafer is covered with patterns. This system utilizes reticle to create patterns. Virtually all sub-micron semiconductor exposure is done by some type of stepping exposure system.

Step and Scan - a step and scan system steps to different locations on a wafer for exposure similar to a step and repeat system, except a step and repeat system exposes a whole area at once and a step and scan system scans light through a slit across the area to be exposed. Difficulties in manufacturing large lens with high resolution limit step and repeat lens systems to approximately 25 x 25mm exposure areas, referred to as fields. Step and scan can produce an approximately 25mm wide field but then scan to a length of approximately 35mms.

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