Glossary

Integrated Circuit (IC)

An electronic circuit incorporating electronic devices (transistors, diodes, resistors, capacitors, etc.) formed into an integral block on a semiconductor wafer.
There are five basic advantages when ICs become more highly integrated:

Products incorporating ICs are smaller in size and lighter in weight
Reduced power consumption
Faster response rates
Higher reliability
Lower prices

Liquid Crystal Display (LCD)

Display devices make good use of the characteristics of liquid crystal. The narrow gap between two thin sheets of glass is filled with liquid crystal, and when voltage is applied to the electrodes installed on the inside surface of the glass substrate, the polarity of the liquid crystal molecules changes. This, in turn, changes the transparency of the liquid crystal. The display panel is divided into tiny regions called pixels, and the transparency of each pixel is individually controlled to display letters or images. Liquid crystal does not emit light, so the light source for the display is either incoming light reflected by the LCD panel, or a backlight mounted behind the liquid crystal. LCD displays are generally classified as either simple matrix LCD (STN, etc.) or active matrix LCD (TFT, etc.), depending on how current to the display is controlled, and the type of display required depends upon the application.

Mother glass

An extremely thin glass plate that is used in manufacturing the displays of LCD TVs, notebook computers, etc. Mother glass sizes are gradually increasing: the 10th generation size is 3.13 x 2.88 meters.

NA (Numerical aperture)

Normally used in its abbreviated form, NA defines lens brightness as NA = n x sin alpha, where alpha is the angle of incidence of the most oblique light entering the lens, and n is the refractive index of the lens. NA is a key parameter in determining stepper resolution.

nm (nanometer)

A unit of length equal to 1-billionth of a meter (1/1,000th of a µm).

Photomask

The plate containing the template pattern that is used to form or etch a circuit onto a silicon wafer using an IC stepper or onto a glass plate using an LCD stepper.

Resolution

Resolution is a value indicating the degree of intricacy of a pattern to be transferred onto a wafer in the photolithography process. The resolution ( R ) for steppers can be expressed as R = k₁ multiplied by lambda/NA, where the wavelength of the light source is represented by lambda and the lens' numerical aperture by NA. Plainly stated, the resolution of a pattern increases when a light source with a shorter wavelength is introduced, and/or when a lens with a higher numerical aperture is employed.

Throughput

Generally, throughput is a value that indicates processing capability within a fixed period of time. Here it indicates the number of wafers an IC stepper can process or the number of panels an LCD stepper can process within a fixed period of time.

Example:: IC stepper throughput: 140+ wafers (300mm) per hour; LCD stepper throughput: 480 panels (46 inches wide) per hour