Oktolex™ Tailored Membrane Technology

In July 2017, Entegris launched Oktolex™ membrane technology to improve yield in ArF, KrF, and EUV lithography for Advanced Logic, DRAM, and 3D NAND Devices. Each Oktolex membrane is tailored to target the specific defect-causing contaminants of each unique photoresist or photochemical.

Specific “killer-defects”, such as micro-line-bridges are one of the key challenges in photolithography’s advanced applications, such as multi-pattern. They generate from several sources and are very difficult to eliminate. Point-of-use filtration (POU) plays a crucial role on the mitigation, or elimination, of such defects.

Controlling contamination in the most advanced logic and memory applications requires a multi-disciplinary approach

In sieving (size exclusion) removal, particles too large to pass through the pore structure of the membrane are captured either on the surface or in smaller passages inside of the structure. The smaller the pore size, the better the sieving efficiency will be.

Non-sieving removal is related to the adsorption of particles to the membrane surface and is independent of particle or pore size. A variety of inter-molecular forces govern the interaction between the particle in solution and membrane surface such as electrostatic forces, Dipole forces, London forces, etc. As long as the particle can approach the membrane surface and experience a net attractive force, it will be captured.

The Oktolex membrane technology is an effective tool to improve membrane wetting properties, filtration efficiency and contaminant selectivity using both sieving and non-sieving removal mechanisms. The tailored membrane technology enables precise contaminant targeting without negative impact on the chemical composition in a variety of lithography techniques and process materials.

Defect Study


Defect library used in this work.



Normalized Defect Pareto