After quartz blanks with various sulfate ion amount on the surfaces were exposed by an ArF laser, growing defects, haze,
on the surfaces were consequently counted by an inspection tool. As a result, the number of haze largely depends on the
sulfate ion amount, and it is found that no haze is generated when the sulfate ion amount is smaller than a threshold value.
A new haze generation model is provided to explain the threshold phenomenon. And then storage impact on increase of
the sulfate ion amount was investigated. The sulfate ion amount increases with storage time and airborne SOx
concentration. From the results, the adsorption coefficient of an extended Langmuir equation was calculated, and the
adsorption phenomenon was analyzed in detail. Simulation results show that it is recommended, regarding for storage
environment, to keep under 0.01 ppbv airborne SOx concentration in order to prevent haze for one year.
After quartz blanks with various sulfate ion amount on the surfaces were exposed by an ArF laser, growing defects, haze,
on the surfaces were consequently counted by an inspection tool. As a result, the number of haze largely depends on the
sulfate ion amount, and it is found that no haze is generated when the sulfate ion amount is smaller than a threshold value.
A new haze generation model is provided to explain the threshold phenomenon. And then storage impact on increase of
the sulfate ion amount was investigated. The sulfate ion amount increases with storage time and airborne SOx
concentration. From the results, the adsorption coefficient of an extended Langmuir equation was calculated, and the
adsorption phenomenon was analyzed in detail. Simulation results show that it is recommended, regarding for storage
environment, to keep under 0.01 ppbv airborne SOx concentration in order to prevent haze for one year.
Photomasks with various sub resolution assist feature (SRAF) were vigorously cleaned by a megasonic tool, and their
pattern damage, "SRAF-missing", was investigated. As a result, it was found that SRAF-missing can occur at a low
probability by the megasonic cleaning and the probability significantly depends on SRAF size, especially width. With
smaller than 100 nm width, SRAF-missing probability rapidly increased with SRAF width reduction. In addition, the
relationship between SRAF-missing and acoustic pressure was investigated, and at the same time that between particle
removal efficiency (PRE) and acoustic pressure was also investigated. As a result, SRAF-missing and PRE showed a
trade-off relationship. Using all results, an experimental equation was provided. After verification by additional
experiments, some simulations were done, and megasonic cleaning subject was predicted for the 45nm and 32nm-node
mask fabrication.
We investigated that the root cause of the crystal growth on the reticles at 193nm excimer laser lithography. We confirmed that crystal growth consisted of ammonia sulfate. We investigated the relationship between crystal growth and 3 factors; reticle cleaning condition, exposure environment, and storage environment. We reduced the residual sulfate ion on mask surface by optimizing cleaning condition. On the evaluation of the wafer fab, total exposure energy until crystal growth occurred were increased as residual sulfate ion is reduced by the cleaning condition optimization. In order to evaluate influence of exposure environment, we carried out an irradiation test under mixture of oxygen and nitrogen up to 10kJ/cm2. We did not observe crystal growth up to 10kJ/cm2. We suppose that crystal growth might be prevented by controlling chemical environment. Regarding storage environment, amount of sulfate ion on the mask surface was increased when it was stored in certain kind of box. Out-gas from storage box is one of sulfuric ion source.
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