Design of Refractive/Diffractive Hybrid Projection Lens for DMD-Based Maskless Lithography

The projection lens is the core component of DMD-based maskless lithography and its imaging quality directly affects the transferal of exposure pattern. Based on the traditional projection lens system, we have designed diffractive optical element (DOE) and aspheric surfaces to optimize the refractive/diffractive hybrid projection lens system to improve its imaging quality. We found that the best effect is obtained when DOE is very close to the front lens group before the diaphragm of the hybrid system. Compared with the traditional projection lens system, this hybrid projection lens system has lower wave aberration with the help of DOE, and higher image quality owing to the modulation transfer function (MTF) value being improved. Finally, a hybrid projection lens system with working distance of 29.07 mm, image Space NA of 0.45, and total length of 196.97 mm is designed. We found that the maximum distortion and field curvature are 1.36 × 10−5% and 0.91 μm, respectively.

Maskless Lithography Using Silicon Oxide Etch-Stop Layer Induced by Megahertz Repetition Femtosecond Laser Pulses

In this study we report a new method for maskless lithography fabrication process by a combination of direct silicon oxide etch-stop layer patterning and wet alkaline etching. A thin layer of etch-stop silicon oxide of predetermined pattern was first generated by irradiation with high repetition (MHz) ultrafast (femtosecond) laser pulses in air and at atmospheric pressure. The induced thin layer of silicon oxide is used as an etch stop during etching process in alkaline etchants such as KOH. Our proposed method has the potential to enable low-cost, flexible, high quality patterning for a wide variety of application in the field of micro- and nanotechnology, this technique can be leading to a promising solution for maskless lithography technique. A Scanning Electron Microscope (SEM), optical microscopy, Micro-Raman, Energy Dispersive X-ray (EDX) and X-ray diffraction spectroscopy were used to analyze the silicon oxide layer induced by laser pulses.

ГЕНЕРАТОРЫ ИЗОБРАЖЕНИЙ ДЛЯ БЕЗМАСКОВОЙ ЛИТОГРАФИИ

Многие годы технологи фотолитографии работают на установках проекционной или контактной печати. Им трудно представить, что за последнее время конструктора создали такие лазерные генераторы изображений, которые по точности переноса топологии превзошли все ранее известные способы. Многолучевые лазерные генераторы изображений позволяют на практике внедрять в серийное производство безмасковую литографию. For many years, photolithography process engineers have been operating the tools for wafer projection imaging and tools for proximity exposure. It may be hard for them to imagine the recently designed laser pattern generators which exceed the accuracy of all previously known patterning techniques. Multichannel laser pattern generators make it possible to introduce maskless lithography into mass production.