Review of near and long term extension challenges for EUV lithography at 0.33 and 0.55NA. Focus on mask and infrastructure gaps + opportunities and a review of progress made in critical areas to support EUV extension.
This past year has witnessed a sharp increase in EUV lithography progress spanning production tools, source and infrastructure to better position the technology for HVM readiness. While the exposure source remains the largest contributor to downtime and availability, significant strides in demonstrated source power have bolstered confidence in the viability of EUVL for insertion into HVM production. The ongoing development of an EUV pellicle solution alleviates industry concern about one significant source of line-yield risk. In addition to continued expected improvements in EUV source power and availability, the ability to deliver predictable yield remains an ultimate gate to HVM insertion. Ensuring predictable yield requires significant emphasis on reticles. This includes continued pellicle development to enable the readiness and supply of a robust pellicle solution in advance of 250W source power, as well as improvements in mask blank defectivity and techniques to detect and mitigate reticle blank and pattern defects.
As the design rules and the actual sizes of the patterns being printed continue to shrink well below half the wavelength of light being utilized, the budgets associated with all variations in imaging likewise continue to squeeze to tighter required tolerances. In this environment, the control and adjustment of the imaging has continued to increase in importance. Building upon previous work in the field of lens adjustment and optimization, additional methods have been developed and implemented which enable more specialized adjustment towards the optimization of given priorities associated with a given patterning step. Specifically, it is fast becoming typical to leverage all available degrees of adjustment freedom uniquely for each critical layer identified in a given process. Various optimization goals are discussed, with procedures and results presented for each. Examples of these include: 1) optimization of a single machine towards the best possible ultimate CD uniformity performance while staying within a specified range of allowed residual distortion 2) optimization of ultimate distortion magnitude, while staying within a budgeted level of imaging/CD uniformity performance 3) optimization of specific aberrations while maintaining all others within budgeted levels of allowed magnitude The motivations driving each of these sorts of optimizations will be discussed, as well as limitations that may exist from various sources, including metrology, process variation and it effects, and the imaging tool. The impact such optimization capability can have on the defined CD budget will also be discussed, towards the goal of qualifying and, where possible, quantifying the overall improvement possible through application of these optimization techniques. These sorts of improvements and their documentation can allow for feedback into the device design process, leveraging the reduced level of variation resulting from such optimizations.
Tilt in the optic axis of the illumination system with respect to the projection lens manifests itself as a shift of the illumination source intensity distribution in the pupil plane of that projection lens. The impact of this error category upon various types of patterns and among various imaging configurations is studied through image simulation as well as experiment. Issues addressed will include:-Methods of measuring illuminator tilt -Sensitivity of sample cases to illumination tilt, including pattern placement issues as well as pattern fidelity issues -Aberration influence and coupling with illumination tilt influences -Ramifications of illuminator tilt impacts. Finally, comments will be made regarding this error category as it may impact the increasingly stringent process complexities and reducing linewidth sizes required by the processes being developed for the near future.
We present photoluminescence (PL) from Te-rich ZnSeTei_ alloys and ZnSeTei_/ZnTe superlattices
and discuss the growth of these materials on GaSb epilayers on GaSb substrates. We show that growing ZnTe on
GaSb substrates eliminates several bound exciton peaks which occur in ZnTe grown on GaAs. The ZnSeTei_
epilayers show bright luminescence from centers over 100 meV below the expected band edge. PL from ZnSeTe1_
alloys and superlattices is qualitatively very different from PL from CdZni.Te alloys and CdZniTe/ZnTe
We present photoluminescence spectra from CdZnj_Te /ZnTe and ZnSe,,Tei_ /ZnTe strained
layer superlattices grown by MBE, and analyze the band alignments and strain effects. Our results
are based on fitting the dominant photoluminescence peaks to the superlattice band structure obtamed
by k •theory. We find that the valence band offset of the CdZniTe /ZnTe system is quite
small. On the other hand, the photoluminescence data from the ZnSeTei_ /ZnTe superlattices
suggest that the band alignment is type II, with a large valence band offset. We also investigate
the band gap bowing in the ZnSeTej_ alloys, and determine the individual components of the
bowing in valence and conduction bands. Based on our results for band alignments, we evaluate the
prospects for minority carrier injection in wide bandgap heterostructures based on ZnSe, ZnTe, and