Stepper

A stepper is a device used in the manufacture of integrated circuits (ICs) that is similar in operation to a slide projector or a photographic enlarger. Stepper is short for step-and-repeat camera. Steppers are an essential part of the complex process, called photolithography, which creates millions of microscopic circuit elements on the surface of silicon wafers out of which chips are made. These chips form the heart of ICs such as computer processors, memory chips, and many other devices. The stepper emerged in the late 1970s but did not become widespread until the 1980s. This was because it was replacing an earlier technology, the mask aligner. Aligners imaged the entire surface of a wafer at the same time, producing many chips in a single operation. In contrast, the stepper imaged only one chip at a time, and was thus much slower to operate. The stepper eventually displaced the aligner when the relentless forces of Moore's Law demanded that smaller feature sizes be used. Because the stepper imaged only one chip at a time it offered higher resolution and was the first technology to exceed the 1 micron limit. The addition of auto-alignment systems reduced the setup time needed to image multiple ICs, and by the late 1980s, the stepper had almost entirely replaced the aligner in the high-end market. The stepper was itself replaced by the step-and-scan systems (scanners) which offered an additional order of magnitude resolution advance, and work by scanning only a small portion of the mask for an individual IC, and thus require much longer operation times than the original steppers. These became widespread during the 1990s and essentially universal by the 2000s. Today, step-and-scan systems are so widespread that they are often simply referred to as steppers. 1957: Attempts to miniaturize electronic circuits started back in 1957 when Jay Lathrop and James Nall of the U.S. Army's Diamond Ordnance Fuse Laboratories were granted a US2890395A patent for a photolithographic technique that could be used to deposit thin-film metal strips that in turn used to connect discrete transistors on a ceramic plate.