Anti-reflective coatings are used in the lithography process to improve the photoresist
profile and reduce the line width variation caused by scattering and reflecting light. The use of anti-reflective coatings helps improve process operating windows and leads to increased production yields while providing cost effective solutions for advanced semiconductors.
Two Types of Anti-reflective Coatings
Bottom Resist Anti-reflective Coatings
(BARCs) and Top Resist Anti-reflective Coatings (TARCs) improve the photoresist profile and overall process operating window. BARCs are applied prior to the photoresist to help eliminate standing waves and the resulting defective/sloped resist sidewalls, which can commonly occur in imaged nanostructures due to varying and reflected light intensities throughout the resist thickness. BARCS must be selected based on the specific wavelength processes including i-Line, 248nm, 193nm (dry and immersion). They also must be compatible with the photoresist to ensure optimum performance and results. BARCs, which are organic polymer formulations, are applied using a spin-on process and then baked to the recommended temperature.
TARCs are also anti-reflective coatings, however, they are applied on top of the photoresist. Its function is to significantly reduce the amplitude of the resist swing curve during exposure, which helps to provide by critical dimension (CD) control over varying topography, resulting in a wider operating process window. Comprised of water soluble polymers, top-layer anti-reflective coatings are applied to the resist using a spin-coating process after the photoresist softbake. They are also effective in reducing resist defects. TARCs form a protective coating on the resist which also acts as a protective layer that can prevent environmental contamination.
Why Anti-reflective Coatings?
As electronics continue to become smaller, faster and cheaper, enabling ancillaries such as anti-reflective coatings help IC chip manufacturers
produce quality products consistently. From memory and power to microprocessors and hard disc drives, antireflective coatings help enable chip manufacturers ensure optimum IC performance cost effectively.
Optimizing the lithography process, TARCs and BARCs must be matched with the process, substrate and photoresist material. For example, EMD Performance Materials TARCs are well-suited to a broad range of exposure wavelenths and photoresist materials, making them a good multipurpose anti-reflective coating. Additionally, TARCs can be a cost-effective material from a manufacturing process perspective because they're easily removed during the standard photoresist develop step. From a regulatory perspective, EMD Performance Materials’ family of top anti-reflective coatings consists of a unique polymer formulation that's PFOx/telomer free so it meets the most stringent environmental regulations.
EMD Performance Materials BARCs offer superior manufacturing performance benefits based on optimized formulations utliizing industry standard solvent systems and refined polymer components. These formulations allow for custom designed refractive indices of bottom anti-reflective coatings which can minimize reflectivity and maximize swing suppression. Tuned to perform with the desired photoresist, EMD Performance Materials BARCs can improve process windows resulting in improved device yields. Additionally, a wide range of polymer components means more opportunities to optimize performance, including improved etch selectivity and via filling properties while minimizing outgassing and defects.