We demonstrate a technique to print. high-density windows using attenuated phase shift mask, negative photoresist and ArF exposure tool and compare our result with that obtained using a binary mask and positive photoresists.
We report on a novel technique for tuning the illumination of a lithography tool through the use of variable transmission apertures. In conjunction with this illumination technique, we have developed simulation software capable of identifying the optimum source plane coherence and intensity distribution to increase process latitude. This 'system' approach is capable of analyzing features specific to a given device level, or selected subsets of structure types within a given level. The fabrication of the aperture involves selectively depositing (alpha) -C onto a quartz plate that is inserted into the illuminator. Experimental testing has shown this film to be stable in its optical properties with extended exposure to DUV light. A description of the simulation software, aperture fabrication techniques, materials used, and experimental results for several aperture configurations are reported.
The stringent critical dimension control requirements in cutting edge device facilities have placed significant demands on metrologists and upon the tools they use. We are developing a unified, advanced critical dimension scanning electron microscope specification in the interests of providing a unified criterion of performance and testing. The specification is grounded on standard definitions and strong principles of metrology. The current revision is to be published as a SEMATECH document. A new revision, now in progress, will embody the consensus of a vendor/user conference.
When considering optical lithography, there is no true substitute for the resolution enhancements afforded by a reduction in actinic radiation. However, as we move below 365 nm i-line systems, the optics and attendant materials considerations become acute. Additionally, there is an obvious economic impetus to breath new life into existing exposure systems. Various optical enhancement schemes have been developed over the past few years for these and other reasons. While many of these are well suited for the patterns and economics of memories, there are a few that enable sub 0.5 kl ASIC imaging. These include: large NA, optical proximity correction, and the deployment of sub- resolution assist features. We will demonstrate a blend of these that will support 280 nm ASIC pattern delineation with i-line (365 nm) systems and binary (non-phase-shift) masks.
The Hampshire Instruments Model 5000 Stepper is a commercially available laser based 1:1 proximity x-ray stepper. The source of this system is a 25 watt Nd:glass slab laser which is focused to approximately 200 micrometers diameter spot on an iron alloy tape target. Nanosecond pulses fired at a 2 Hz burst (1 Hz average) repetition rate produce slightly more than 1 mJ/cm2 of x-ray flux per pulse at the wafer plane. This flux of soft x-ray has a spectrum of 8 - 20 angstroms centered on the 14 angstroms band. This is the first system shipped by Hampshire Instruments. It is a research and development tool which is not meant for the production line, but rather as a means to investigate issues associated with x-ray lithography and inserting a system of this type into a manufacturing environment. This paper will present final acceptance test results for system resolution, critical dimension control and registration, as well as data showing system performance for the first five months of operation. Results showing 0.2 micrometers line and space resolution across a 14.7 mm field in 1.0 micrometers thick resist printed using a tungsten absorber mask will be presented. Registration test results show a variation of 0.13 micrometers (3 (sigma) ) across a five wafer lot. When the alignment system was slowed down, however, a result of 0.09 micrometers was achieved. Metrology issues dealing with critical dimension control as they pertain to this stepper will be addressed.
Preliminary evaluation of a 1:1 proximity x-ray stepper, built by Hampshire Instruments is discussed here. This stepper, model 5000P, is the first commercial system that uses a laser- generated plasma x-ray source. It was extensively tested at the supplier's facility and in July 1991 it was shipped to AT&T Bell Labs, where its installation is nearly completed.
Many requirements of a point-source x-ray membrane mask are unique, in comparison with masks used with synchrotron sources. Membranes must be thinner, flatter and stronger, for example. We characterize our choices of polysilicon and silicon-rich nitride for membranes, and a simplified one-piece (monolithic) mask blank. We use a dual strength testing technique which discerns whether membrane strength is limited by defects in the film growth process, or defects in the attachment of membrane to support. We find our membrane films are stronger than previously thought, and that improvements in membrane/support attachment will effect a more durable membrane mask.
We report improvements in optical and mechanical properties of x-ray lithography masks based on polycrystalline
Si membranes. The optical transmittance of polycrystalline Si was increased to match that of single crystalline Si in 0.6
to 0.9 j.tm spectral range. This was accomplished by modifying deposition temperature and gas composition during
LPCVD film growth. The new films are intrinsically tensile, allowing formation of taut membranes on crystalline Si
substrates and on glass disks that are matched in thermal expansion to Si, in contrast to earlier polysilicon films which
required thermal expansion mismatch. The mechanical integrity of the masks was further improved by direct deposition of
Si on thick machined glass disks, thus eliminating bonding of thin substrates to rigid support rings. The monolithic
mask blanks are considerably more flat than the bonded structures, either single- or polycrystalline.