As the nano-lithography technology continues to develop towards advanced generation of ArF immersion lithography,
the quality of ArF EAPSM becomes the most valuable factor for worldwide Maskshop. Therefore outturn of ArF
EAPMS increase continuously, and people who work in the fields of semiconductor engineering give consequence to
good quality of ArF EAPSM until the EUV lithography generation. Because 300mm wafer litho-facility use higher
exposure energy, wider shot field and more shots per a wafer for achieving more memory(DRAM or Flash) chips than
200mm exposure facility, photo engineer wants unchanged initial condition of mask quality(CD MTT, CD Uniformity,
repeating defect, phase shift and transmittance). In other words, mask manufacturer must focus on the concept of ArF
EAPSM 'life time'.
We have investigated the influence grade inducing the lithographic variation between the growth of exposure energy
based Haze phenomena, thin organic pellicle membrane characteristics, and we have verified that the ArF pellicle
durability is one of the most important evidence for improvement of life time of ArF EAPSM.
In this study, related with ArF EAPSM life time, we tried to evaluate the influence of ArF pellicle characteristic
consisting of pellicle membrane transmittance strength (durability against ArF laser source) and non acid mask condition
for the period of non Haze contamination without added re-pellicle → re-cleaning cycle. Metrological inspection and
evaluation was conducted with several equipment and analysis including mask inspection, Scatterometer, IC, ArF laser
Backside defects a few micrometers in size are serious concern in lithography because they can degrade the image
quality on a wafer. It was known that defects attached on the backside affected the printing images on a wafer by locally
altering the partial coherence (σ) and the transmitted intensity of the illumination. The ability to detect and to simulate
their impact of defects on the backside is one of the key components in ensuring quality of photomask.
The purpose of this study is to determine the minimum size of defects on the backside which would be affected
printability in 193nm photolithography. It was investigated to the influence of wafer critical dimension (CD) variation
according to illumination and NA, that of refraction according to defect size.
For this study, a reticle was designed to include line and space patterns, contact patterns and isolated patterns on the front
side. And the type of defects attached on the backside was made of chrome to investigate the relation between
transmittance of backside defects and its printability.
The correlation of measurements made with UV and DUV-based inspection system; simulation performed with a
193nm aerial image measurement system. Besides the allowable size of backside defects was determined using the
criterion of a maximum intensity variation of 10%.
We have investigated the factors having influence on the lithographic fidelity variation in 193nm masks. Significant
researches have been studied that haze contamination, resulting from the absorption of chemical residual ions and mask
container out-gassing in mask fabrication, is one of the major component to reduce the optimized lithography condition
such as Best Focus, Depth of Focus and Exposure latitude of individual feature. And also environment being containing
humidity, ambient AMC (airborne molecular contamination) react with high exposure energy to form crystal growth of
ionic molecular complex such as ammonium sulfate causing abnormal printability. Moreover, optical issue of organic
pellicle membrane is thoroughly considered that perfluoro polymer degradation induced by high photon energy affect the
transmittance intensity. Consequently, these photophysical alterations bring about the lithographic variation and cause
considerable defects in wafer printing.
In this paper, we tried to verify the influence grade inducing the lithographic variation among the latent contamination
factors consisting of mask back-side quartz contamination, the growth of exposure energy based haze phenomena, thin
organic pellicle membrane degradation and modified character of MoSiN surface. Metrological inspection and
photochemical reaction evaluations were conducted with several equipments including AIMS, Scatterometer, XPS, SIMS,
FT-IR, UV, ArF acceleration laser to demonstrate the proposal mechanism of correlation between lithographic variation
and latent contamination factors. The optical issues and lifetime of ArF PSM were simulated with the evaluation of
effects of pellicle degradation and surface modification.
In sub-60nm technology node, cleaning process becomes specialized to clear the defects without pattern damage as
decreasing critical particle size to control. While cleaning process has to meet the primary requisite, removal of particle
including organic residue and prevention of particle re-deposition, it should enable to suppress haze phenomena for a
long life of photomask. However, to solve the problem of haze, the chemical materials caused haze seed should be
hardly used and physical force becomes strengthen as the compensation for cleaning efficiency. Unfortunately it brings
about another problem, pattern damage seriously.
In this paper, adequate cleaning conditions which are applicable in sub-60nm technology node are evaluated to meet the
dilemma among three requirements, high cleaning efficiency, and prevention of pattern collapse, and prevention of haze
phenomenon. All cleaning steps in photomask process were set up using only 172nm UV irradiation for degradation of
organic contaminants and deionized water (DI) with acoustic power for particle lift-off. The effect of UV and DI
cleaning on cleaning efficiency and haze phenomena was derived from carrying out chemical and physical analysis
simultaneously. Also, we could quantify the statistical probability of pattern collapse in each of technology node and
layer shape as different condition of megasonic frequency and its power. As a result, it was known that this cleaning
process have various merits to make out dilemma mentioned above, if it satisfies optimized conditions.
The ability to eliminate the critical source of haze contamination which can be derived from the cleaning chemistry residues and mass production environment has become a major challenge for 193 nm photolithography in semiconductor industry. Furthermore, as the specification for pattern generation on photomask becomes tighter, it is getting harder and harder to eliminate defects with both minimal structural damage and preservation of photophysical properties. We designed for the smart cleaning strategy to achieve the <b><i>defect-free photomasks</i></b> as a concern of above current issue with a combination of well-known cleaning technology, such as using the collective effects of ozonated water (DIO<sub>3</sub>) for the alternative to conventional clean (SPM/SC1) and UV/O<sub>3</sub> treatment for the control of sulfate concentration. In addition to photomask clean, these strategies are also used for photoresist stripping.
As well as the final cleaning process, it is a rational strategy that judicious modification of inter-process clean. Specially, that kind of view is focused on the after-development clean (ADC) process which mainly eliminated the source of fatal defects on the mask, such as pattern bridge following dry etch process.
In this paper we will propose a novel cleaning strategy for the elimination of potential source of haze formation and fatal defects.
This is an experimental result for the inhibition of effects of the growing defect. Up to now, it has been considered and defined that the growing defect is an unexpected and unusual reaction by bonding impure ions existed on the mask each other. This study is not only to suppress the unexpected reaction when making the final mask but also to stabilize the surface of mask by controlling by-product occurred when stripping upper Cr layer and damaged layer from sputtering process. According to the analysis of the surface roughness stemming from each process (from wet etching to cleaning Process) of MoSi layer, the surface still comes to be rough when a mask is done through all process. So, heat treatment was performed and surface roughness was measured to figure out how much the surface condition would be improved and how many remaining SO4, NH4 Ions on the surface after cleaning process reduced. This study shows the major factor causing plasma damage is a dry etcher, a way to control the damaged layer of MoSi at PR strip process, the level of stabilization of mask surface through cleaning process and a clue to be able to prove the stabilization by adding specific process. Analysis tools for this study are as follows. AFM (for checking the roughness of surface), TEM (for checking cross-section) and IC (Ion chromatography)analysis equipment.