Unpolarized light has traditionally been used for photolithography. However, polarized light can improve contrast and exposure latitudes at high numerical aperture (NA), especially for immersion lithography with an NA > 1.0. As polarized light passes through a reticle, any birefringence (BR) in the reticle material can cause a change in the orientation or degree of polarization, reducing the contrast in the final resist image. This paper shows the effects of reticle BR on dry and immersion imaging for 193nm lithography. The BR magnitude and orientation of the fast axis were mapped across several unpatterned mask blanks, covering a range of BR from 0 to 10 nm/cm. These reticles were printed with a series of open areas surrounded by test structures. The BR was measured again on the patterned reticles, and several locations were selected to cover a range of magnitudes at different orientations of the fast axis. Dry and immersion imaging were evaluated, looking at BR effects on dense lines and contact structures. Mask error enhancement factor (MEEF), line edge roughness (LER), and dose and focus latitudes were studied on line/space patterns. Dose and focus latitudes and 2-D effects were studied on contact patterns. Based upon these results, the effect of reticle BR on CD is minimal, even for BR values up to 10 nm/cm.
A new phase defect repair technique of phase-shifting masks made using conventional chrome-on-quartz blanks is proposed. This technique is based on the planarization of defects and dry etching of the defective area under conditions where the planarization layer etch rate is made equal to the quartz etch rate. The process consists of defining an opening on top of the defective area of the mask in a photoresist layer covering the planarization layer using UV exposure. Phase defects can, therefore, be etched away independent of their three-dimensional profile. An additional advantage of this technique is that the lithography for defect repair and therefore the repair itself is automatically self-aligned to the chrome edge. The feasibility of this process defect repair has been demonstrated using a test mask with programmed phase defects. Wafer printability results show that the defects were effectively removed. This technique has been used to successfully fabricate a phase-shifting mask contact level for a 4 Mbit DRAM product.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.