Customized illumination aperture filter for low k 1 photolithography process

Abstract

A completely new concept for designing the illumination aperture filter is suggested. From experimental or simulative methods, we have extracted the performance of every individual beam component on the illumination plane. The optimal apertures are then obtained by superimposing the best components that meet the requirements demanded by the specific photo processes. Different kinds of optimal apertures were successfully implanted to deal with different process problems. Therefore, it is called the customized illumination aperture filter (CIF). The zero 1D OPE CIF, as a proof of concept, was designed to eliminate the OPE of low k process. Without any OPC, O.6.tm DOF ofthe common ED window was obtained, where ki 0.39 for our NA0.55 stepper to print 0. 18.tm line patterns. To push to smaller ki, another CIF was designed to maximize the individual DOF and overcome the reduced power problem accompanied with the typical aggressive OAI.Using this CIF, we achieved I . Im common DOF with 7% EL for 0. 1 8.tm line patterns. The CIF doubles the power of the Nikon's strong quadrupole, shrinc. An ultimate resolution limit of 0. 1 1.tm line pattern was reached as well with the CIF. Finally, a contact/via CIF was designed combined with a half-tone PSM (6%). The CIF gives about O.8im common DOF with 7% EL for O.2.tm holes and O.7.tm DOF for 0. l7prn holes using thinner resist. The CIF approach is, therefore, proven to be a cost effective and relatively easy realizable alternative to the alternating PSM for extremely low ki process applications.

Evaluating the impact of spherical aberration on sub-0.2-μm contact/via hole patterning

“…The aforementioned discussion suggested the best focus shift in dense hole pattern can be suppressed by a larger portion of lens utilization. Hence, we can customize the illumination configuration to provide better lens utilization without much sacrifice of DOF 10,11 . Figure 13 shows the design of customized illumination, which can be regarded as the combination of conventional highly coherent illumination and quadrupole illumination.…”

Customized illumination aperture filter design for through-pitch focus latitude enhancement of deep submicron contact hole printing

“…The idea of this graphic method has been disclosed in several previous works for source and mask optimization but lacked the detailed derivation of the diagram. [8][9][10][11][12] Here we will give an instructive interpretation of the physical meaning of the illumination chart method and elucidate its application on source element selection. Figure 2 shows the concept and geometry involved in the illumination chart construction, which is the reverse thinking of source-image plots in Fig.…”

“…[10][11][12] With regard to a balanced through-pitch lithographic performance, the attenuated PSM approach is a more potential candidate to cooperate with modified illumination methods because of its well-known effectiveness in enhancing the imaging performance of isolated patterns. 13,14 The combination of modified illuminations with attenuated PSMs has been tested experimentally for contact-hole patterning, 6,9,[15][16][17] but few discussions were drawn on the mask-specific optimization of illuminations.…”

“…6,7 With this modified illumination technique, a satisfactory common process window for one-dimensional line/space patterns can be achieved using a conventional binary mask. 8,9 When it comes to two-dimensional window patterns, due to the complexity of the diffraction nature, additional mask shape modification as well as phase-shifting mask ͑PSM͒ technologies are required to manipulate the magnitudes or phases of certain diffraction orders for synergistic combination with a custom illumination scheme. Previous works have described general algorithm of mask and source optimization for two-dimensional regular pattern printing.…”

Extending SMO into the lens pupil domain

“…Gau et al proposed the Archel method, which divides the source into regions with the same collected diffraction orders, and then selects the source regions based on an imaging quality metric, such as depth of focus (DOF) [1]. Rosenbluth et al used a Fourier Transform method to calculate the mask pattern that provides the optimized wave front, thus performing joint source and mask optimization.…”