Multilayer Systems

​OptiStack® multilayer systems are our flagship lithography technology, and are used for leading-edge high volume IC manufacturing.

OptiStack® multilayer lithography systems are designed for the most advanced high-volume semiconductor manufacturing processes in the world. Our versatile OptiStack® material set is designed to be used in combination with our proprietary optical modeling to achieve the finest resolutions possible with 193-nm immersion lithography.

The OptiStack® system advantage

A universal substrate – OptiStack® materials work together to planarize a wide range of topography, effectively creating a "universal substrate" for advanced processes.

Superior optical performance – OptiStack® modeling systems work with unique paramaters to yield superior pattern fidelity to that of standard modeling systems.

High aspect ratio capabilities – OptiStack® materials maintain excellent pattern fidelity even at extreme aspect ratios.

How OptiStack® multilayer systems work

OptiStack® multilayer systems use a combination of a thick, carbon-rich underlayer, a thin silicon hardmask, and a thin photoresist to achieve accurate pattern transfer to the substrate. Some scenarios also require an additional bottom anti-reflective coating (BARC) beneath the photoresist.

After the thin photoresist is imaged, the pattern is transferred to the silicon hard mask (Si-HM, also known as a spin-on glass or SOG) using a highly selective etching process, such as fluorinated plasma. The pattern is then transferred to the carbon-rich underlayer (known as a spin-on carbon or SOC) with another selective etching process, typically an oxygen-rich plasma. The imaged hardmask and SOC layers can then be used to transfer the pattern to the substrate.
Optistack Process Flow - OptiStack® Multilayer

Why we need multilayer lithography systems

Immersion lithography requires the photoresist to be extremely thin due to the shallow depth of focus inherent in high-NA optical systems. At these thicknesses, the photoresist can no longer survive the etching steps required to transfer the pattern into the substrate. The additional materials in a multilayer stack essentially work to magnify the etch resistance of the photoresist.