The reduction of wavelength in optical lithography and the use of enhancement techniques like phase shift technology, optical proximity correction (OPC), or off-axis illumination, lead to new specifications for advanced photomasks -a challenge for cost effective mask qualification. "Q-CAP", the Qualification Cluster for Advanced Photomasks, comprising different inspection tools (a photomask defect inspection station, a CD metrology system, a photomask review station and a stepper simulation software tool) was developed to face these new requirements. This paper will show the performance and reliability of quality assessment using the Q-CAP cluster tool for inspection and qualification of photomasks. Special attention is paid to a key issue of mask qualification: the impact of CD deviations, loss of pattern fidelity -especially for OPC pattern and mask defects on wafer level.Photomasks were produced containing patterns with pre-programmed defects. Wafers were processed using these testmasks. Results from inspection of these wafers are compared to predictions of different cluster tools gained during inspection of the photomasks. One aspect covered in the paper is the comparison of CD-SEM images from wafers to software stepper simulation results: aerial image and printed wafer pattern using OPTISSIMO® Client (without and with resist model respectively).The Q-CAP cluster concept allows the combination of hardware tools as well as software tools via network communication. It is designed to be open for any tool manufacturer and mask house. All mask relevant information created during processing a photomask is stored to a SQL database and is available for all tools connected to the cluster. The cluster can be seen as one single virtual tool that facilitates full qualification of photomasks. First results using a prototype of the Q-CAP cluster in production are presented.
To enable lithography at low ki factors, OPC (optical proximity correction) on photo masks is a method of strong and growing importance. But CD (critical dimension) metrology ofOPC features is suffering from several drawbacks: -oPc structures often do not have two parallel edges, which are required for usual CD metrology methods. -There are no commonly agreed standard definitions how and where to measure some types of OPC structures. -The CDs are very small (often far below the lower limit ofCD standards). -There is no automated software for the measurement of OPC structures on operator level.A metrology method and a fully automated software for metrology of OPC structures based on LWM optical CD metrology tools is shown in this paper. It automatically distinguishes between hammerheads and serifs in various orientations. The method works analog to pitch measurements and requires only pitch calibration and no additional CD calibration. The results of light optical metrology tools with i-line and DUV wavelength is compared to CD SEM results.
A comparison has been made in terms of mask CD linearity measurements between the 2 tool versions of a 248nm based optical CD metrology tool for photomasks, i.e., the high-NA M5k-SWD and the through-pellicle M5k-LWD, as well as to a reticle SEM, i.e., the KLA-T 8250-XR. The measured pattern consists of lines and dots (dark features), and spaces arid contact holes (clear features), both in equal-lines-and-spaces and as isolated feature. Two masks have been measured with the same test pattern, i.e., a binary and a 9%-attPSM for 193nm lithography. The latter was especially challenging because typically such embedded phase shift masks are much more transparent at higher wavelengths than those for which they are optimized. All measurements on the M5k were made intentionally before calibration (apart fmm pitch calibration). The resolution performance of the M5k-LWD and the measurement offsets found between M5k and SEM, as well as between the two M5k-versions is discussed. In addition, two-dimensional metrology based on feature contour extraction from optical or from SEM images has been compared. Although its resolution is inherently lower than that of the high-NA M5k-SWD and a reticle SEM, the M5k-LWD offers a possibility to extend such assessment to pelliclized reticles, which is not possible on the alternative tools.
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.
customersupport@researchsolutions.com
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.