Photoresist is light-sensitive material used in the manufacture of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). Processes such as photolithography and photoengraving form a patterned coating in the photoresist film.
Predominantly used in the manufacture of integrated circuits and flat panel displays, photoresist can be positive or negative. Positive photoresist becomes soluable when exposed to UV light, whereas negative photoresist becomes crosslinked and insoluable when exposed to UV light. Photoresist is applied
to the surface of a wafer that has been treated with HMDS, which is a commonly used adhesion promoter to ensure the photoresist adheres properly to the wafer substrate. The most common method of applying photoresist is spin coating to achieve a thin uniform coating across the wafer. However, depending on the substrate and/or application, other photoresist application techniques may be used such as spray or extrusion coating.
Where is photoresist used?
Photoresist material for the integrated circuit industry is used for a variety of lithographic processes covering a wide range of exposure tools and processes. Applications range from sub-micron geometries to thick film applications. Photoresist materials can be applied to a large variety of substrates.
In the flat panel display industry, photoresist materials can also be used in a wide range of processes. Applications extend beyond the 5th generation spin coating, into advanced slit-coating processes. Photoresist materials are also available for roller coating and extrusion coating.
Photoresist and Innovation
As more complex lithographic patterning evolves, the need for advanced photoresist
materials grows. Manufacturers are combining innovative process techniques and ancillary photoresist chemicals to further enhance photoresist performance and allow for improved imaging. For example, anti-reflective coatings
improve the photoresist profile while reducing line width variation and increasing overall process windows. Innovative spin-on organic polymers (BARCs) can improve photoresist profiles at specific lithographic wavelength processes including i-Line, 248nm, 193nm and 193nm immersion.
The results can include faster etch rates and a wider operating process window, which lead to greater throughput and enable innovation. Thanks to photoresist and ancillary enhancements, advanced lithography techniques such as double patterning using 193nm immersion lithography tools are made possible.
Photoresist and Manufacturability
Innovations in manufacturing techniques and the use of chemically amplified (CA) photoresist have helped manufacturers achieve efficiencies necessary to manufacture cost effectively at submicron levels. Also, the introduction of key enabling ancillary products, including the use of anti-collapse rinse
products, provides a wider process window for 193nm photoresist material while reducing the overall defect levels, resulting in higher yields.
Advances in photoresist
Advances in lithographic process technologies continue to influence innovation in photoresist material. Ongoing research explores ways to further improve the imaging and mechanical properties of photoresist material.