To meet shrinkage demands of device pattern size, a new platform ArF exposure tool , NSR-S308F, has been developed with an extremely high NA projection lens. This equipment has been developed not only for ensuring better imaging of dry ArF, but also for achieving imaging enhancement of immersion ArF. To satisfy imaging and overlay accuracy requirements for 65nm node lithography, the heat management, body stiffness, and reaction force canceling system have been drastically improved. Optimized illumination conditions and polarized illumination1 have been developed to expand the severe process margin for ArF dry exposure tools. In addition, some applications support: the maximization of imaging performance of S308F; the aerial image measurement function2 to correct aberration of projection lens; the optimization software of lens aberration in a specific device pattern, and special software to realize excellent mix and match accuracy. Latest evaluation results and the improvement items of S308F will be presented.
The severe mask specification makes mask cost increase drastically. Especially, the increase in the mask cost deals ASIC businesses a fatal blow due to its small chip volume per product. Pattern writing cost has always occupied the main part of the prime mask cost and the emphasis of this is still increasing. This paper reports on a Photomask Repeater strategy to be a solution for reducing mask cost in pattern writing, comparing with conventional EB system.
Device masks for 180nm lithography was fabricated by PR system. These masks were verified by device yields comparing with masks written by other conventional systems. There were no differences in device yields between PR system and conventional system. Fine analysis of CD error was carried out for enhancement of CD uniformity to apply Photomask Repeater to 130nm lithography. It revealed that major CD error function is global CD error. By optimizing exposure dose of each shot to compensate global distribution, global CD error was reduced from 7.9nm to 5.5nm. Finally, CD uniformity of 8nm was achieved. PR system can afford to fulfill the requirement of CD uniformity for 130nm lithography. Simultaneously, the result of fine analysis indicates excellence of PR system in littleness of random error.
A Device mask of 180nm generation was fabricated by Photomask Repeater system and the performance of it proved to be high by the results of fabricated mask. Great margins between the results of the fabricated mask and specifications suggest that lower graded masks can be used as master masks. From this point of view, error budgets were estimated about CD uniformity and pattern placement. The required specifications for master mask were estimated for 180nm and 130nm lithography. In CD uniformity the specification is 50nm(3?) for 180nm and 30nm(3?) for 130nm lithography. In pattern placement the specification is 75nm(3?) for 180nm and 50nm(3?) for 130nm lithography. In defect size the specification is lOOOnm for 180nm and 900nm for 130nm lithography. The requirements of master mask are rather rough even for 130nm lithography and enough realistic.
We have developed a new mask patterning system, which can fabricate 130nm generation masks by means of a stitching exposure technique. We call this system the Photomask Repeater (PR)1,23,4. The PR is a 5x i-line stepper modified for mask manufacturing with a field size of 22x22mm in a single exposure. However, the device size on a 4x mask is larger than 22x22mm. Furthermore, excellent mask CD uniformity is required. For this purpose the exposure field size was extended with the use of “seamless stitching technology”. This is clearly the key to obtaining a practical, accurate mask patterning system. Results have been achieved on masks with this system showing CD variation of less than +/- 7nm at a stitching area by means of a “gradation filter”. Moreover, overall CD uniformity is 10.36nm (3?), while image placement accuracy is 17.8nm (3?) and 2nd alignment accuracy is 24.1nm (3?). PR is an attractive system for System on Chip mask manufacturing, and is also effective in reducing Turn Around Time.
KEYWORDS: Photomasks, Optical proximity correction, Semiconducting wafers, Critical dimension metrology, System on a chip, Lithography, Printing, Kinematics, Scanning electron microscopy, Process engineering
New pattern generation system, Photomask Repeater, based on i-line stepper has been developed. This system can transfer device patterns from master masks onto a photomask plate with 22mm field size. To print a chip larger than the 22mm field, stitching technology has been developed. Critical dimension error in the region where fields are stitched is the key issue of this technology. Quantification of critical dimension deviation induced by field misplacement was carried out by calculation. Introducing exposure dose gradation, it was reduced less than 1.5nm. From measurements of a real exposed mask this technique proved to be able to stitch fields seamlessly. Major two specifications, pattern placement accuracy and critical dimension uniformity, were evaluated. Both specifications required for 150nm photomasks were fully satisfied. Availability of the photomask repeater to memory device and system on chip is discussed.
KEYWORDS: Reticles, Photomasks, Critical dimension metrology, Manufacturing, System on a chip, Optical proximity correction, Mask making, Semiconducting wafers, Digital signal processing, Fabrication
We have developed a new reticle exposure system, which can fabricate 150nm generation masks by means of a stitching exposure technique. We call this exposure system the Photomask Repeater, or high accuracy repeater (HR). HR is a modified i-line stepper for mask manufacturing with a field size of 22 by 22 mm in a single exposure. However, the device size on a 4x mask is larger than 22 by 22 mm. Furthermore the improvement in mask CD uniformity is required. For this purpose the exposure field size was extended with the use of 'seamless stitching technology'. This is the key to obtaining a feasible exposure system with the use of this method. Results have been achieved with this system showing CD variation of less than +/- 5 nm across a 1D seam band by means of a 'gradation filter'. Moreover, overall Cd uniformity is less than 13nm, while image placement accuracy is less than 24nm. HR is an attractive system for SoC mask manufacturing, and is also effective in reducing TAT.
New pattern generation system, Photomask Repeater, based on i-line stepper has been developed. This system can transfer device patterns from master masks onto a photomask plate with 22mm field size. To print a chip larger than the 22mm field, stitching technology has been developed. Critical dimension error in the region where shots are stitched is the key issue of this technology. Quantification of critical dimension deviation induced by shot misplacement was carried out by calculation. Introducing exposure dose gradation, it was reduced less than 1.5nm. Form measurements of real exposed mask this technique proved to be able to stitch shots seamlessly. Major two specifications, pattern placement accuracy and critical dimension uniformity, were evaluated. Both specifications required for 150nm photomask were fully satisfied. Availability of the photomask repeater to memory device and system on chip is discussed.
An innovative method of determining best focus with an optical exposure tool has been developed. The method uses wedge shaped marks in photoresist that can be measured automatically. The results show that best focus can be measured with a repeatability of 20 nm. The automatic focus measurement system can be used to characterize lens astigmatism, field curvature and tilt. Data shows good correlation with conventional methods using SEM linewidth measurement.
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