Fotolitografian

Fotolitografian, known in English as photolithography, is a process used in microfabrication to transfer geometric patterns onto a substrate, typically a silicon wafer, by projecting light through a patterned mask onto a light-sensitive resist. The pattern defines features such as transistors, interconnects, and other circuitry.

The technique emerged in the mid-20th century and remains central to semiconductor manufacturing. Advances in light sources, optics, and resist chemistry have improved resolution and throughput. Shorter wavelengths, from visible to deep ultraviolet and increasingly extreme ultraviolet, along with advanced optics and immersion techniques, enable smaller feature sizes and more complex devices.

The core process involves several steps. Substrates are cleaned to remove contaminants. A liquid photoresist is applied by spin coating to form a thin, uniform film, followed by a soft bake to remove solvents. The wafer is aligned with a photomask and exposed to light, transferring the mask pattern to the resist. Depending on the resist type, development removes either the exposed or unexposed regions. A post-exposure bake may follow to stabilize chemically amplified resists. The pattern is then transferred into the underlying layer by etching or by deposition, after which the remaining resist is stripped. Final steps include inspection and cleaning.

Resists come in positive and negative varieties, affecting how patterns are created during development. Photolithography equipment ranges from mask aligners to modern steppers and scanners, and increasingly uses immersion lithography or extreme ultraviolet (EUV) lithography for tighter feature sizes. Applications span integrated circuits, microelectromechanical systems, and microfluidics, while limitations include diffraction limits, cost, and process complexity. Ongoing research aims to push resolution further through new materials and alternative light sources.