Immersion and EUV Lithography: Two Pillars to Sustain Single-Digit Nanometer Nodes

Semiconductor technology has advanced to single-digit nanometer dimensions for the circuit elements. The minimum feature size has reached subwavelength dimension. Many resolution enhancement techniques have been developed to extend the resolution limit of optical lithography systems, namely illumination optimization, phase-shifting masks, and proximity corrections. Needless to say, the actinic wavelength and the numerical aperture of the imaging lens have been reduced in stages, The most recent innovations are Immersion lithography and Extreme UV (EUV) lithography In this presentation, the working principles, advantages, and challenges of immersion lithography are given. The defectivity issue is addressed by showing possible causes and solutions. The circuit design issues for pushing immersion lithography to single-digit nanometer delineation are presented. Similarly, the working principles, advantages, and challenges of EUV lithography are given. There are special focusses on EUV power requirement, generation, and distribution; EUV mask components, absorber thickness, defects, flatness requirement, and pellicles; EUV resist challenges on sensitivity, line edge roughness, thickness, and etch resistance.