As semiconductor technologies move toward 90nm generation and below, contact hole is one of the most challenging
features to print in the semiconductor manufacturing process. There are two principal difficulties in order to define small
contact hole pattern on wafer. One is insufficient process margin besides poor resolution compared with line & space
pattern. The other is that contact hole should be made through pitches and sometimes random contact hole pattern should
be fabricated. Therefore advanced ArF lithography scanner should be used for small contact hole printing with RETs
(Resolution Enhancement Techniques) such as immersion lithography, OPC(Optical Proximity Correction), PSM(Phase
Shift Mask), high NA(Numerical Aperture), OAI(Off-Axis Illumination), SRAF(Sub-resolution Assistant Feature), mask
biasing and thermal flow. Like this, ArF lithography propose the method of enhancing resolution, however, we must
spend an enormous amount of CoC(cost of ownership) to utilize ArF photolithography process than KrF.
In this paper, we suggest the method of contact holes patterning by using KrF lithography tool in 90nm sFlash(stand
alone Flash)devices. For patterning of contact hole, we apply RETs which combine OAI and Model based OPC.
Additionally, in this paper we present the result of hole pattern images which operate ArF lithography equipment. Also,
this study describes comparison of two wafer images that ArF lithography process which is used mask biasing and Rule
based OPC, KrF lithography process which is applied hybrid OPC.
As the resolution requirement downing 90 nm beyond, hole pattern is one of the most challenging features to print in
the semiconductor manufacturing process. Especially, when hole patterns have dense array of holes as they are consisted
of several columns with single row, there can be serious distorted form from desired patterns such as oval hole shape and
bridge between holes. It is due to nature of diffraction which generates interaction of diffracted light from near holes.
Overlap margin reduction by hole shape change as oval shape is very harmful in sub-90nm photolithography process
which has very narrow overlay margin. To increase overlap margin, it is necessary to solve these phenomenon. Optical
Proximity Correction (OPC) has been used for overcoming oval hole shape. Through the result of OPC modeling and
simulation, we could get optimized mask bias of hole. Sometimes, good experimental data will be help for this modeling
and OPC process. From these OPC simulation and experimental data, most compatible rule based OPC process could be
developed. In this paper, we suggest the method of improving oval hole shape by using OPC simulation and making rule
base OPC process from experimental data.
Selectivity of extreme ultra-violet lithography mask's material and thickness significantly influences on pattern formation. Since the reflectance changes periodically depending on absorber thickness, we investigated the absorber thickness effect on to near field and aerial image for 32 nm line/space and isolated pattern. We chose germanium and chromium as absorber materials. We also investigated the line width variation by absorber thickness change with different duty ratios. SOLID-EUV of sigma-C was used for this study.