Laser Lithography: An Overview
Laser lithography is a versatile technique for the creation of microstructures such as microelectromechanical systems (MEMS) and integrated circuits. It works on the same principles as photolithography but developments in laser technologies have meant that laser-based manufacturing has become increasingly popular.
Photolithography uses of a photosensitive polymer applied to a surface that is covered with an optically opaque mask. When the polymer is exposed to light, the sections not covered by the mask will harden. The masked areas will remain soft and can easily be etched away. The process is repeated to build up more complex structures.
In computer chip manufacture, photolithography has been the technique of choice as a single resist-covered layer of silicon can be easily converted to hundreds of individual chips. It is possible to create incredibly small and intricate patterns, down to a few nanometers in size.
Different wavelengths of light can be used for photolithography, with UV radiation being a common choice. Originally, lamps were used as a light source, but to make the smallest structures needed for metal-oxide semiconductors lamps have been gradually replaced by lasers.
High-power laser systems, such as CO2 lasers, are excellent tools for precision cutting and machining. The minimum possible feature size that can be manufactured in laser lithography is proportional to the wavelength of light used. The feature sizes achievable are also dependent on the quality and availability of focusing optics and laser beam quality.
There are many technical compromises to be made when choosing optimal wavelengths and laser types for laser lithography. While higher power systems are often desirable for faster machining, thermal load on samples can be a problem and sub-193 nm wavelengths start to be absorbed by air. Instabilities in beam size and shape can also cause issues during the manufacturing process.
Solid state laser systems have proved to be an excellent choice for laser lithography, as they have excellent stability and typically turn-key operation. Modern systems can achieve the high output power necessary for laser lithography in devices robust enough for manufacturing use.
Laser Quantum DPSS Systems
Laser Quantum offers three diode-pumped solid state (DPSS) lasers with a range of output wavelengths designed for laser lithography applications. The gem series is available with 473, 532 and 660 nm output options with excellent power outputs.
By using a combination of hermetic sealing and an active fast feedback system, the gem can achieve outstanding levels of stability in all output beam characteristics. All three systems have a single traverse mode and their small, compact footprint makes them easy to integrate into larger manufacturing platforms.
Key for laser lithography applications, the gem series has a low M2 value and a diffraction-limited beam, so the minimum possible feature size is limited by the wavelength, and not poor focusing or beam conditions. For samples where thermal load may be an issue, the current/power of the system is fully controllable to make complete optimization of the laser lithography process possible.
To request more information or a quotation for this or other Laser Quantum products, contact IL Photonics.