Measurement by AIMS is the final step of mask defect control, and its accuracy is the critical issue to make guaranty and improve the mask quality. AIMS157 has developed by Carl Zeiss SMS GmbH and is expected to make a contribution to accelerate the 157nm lithography technology development. AIMS157 has been challenging to solve 157nm specific optical issues with accuracy for 65nm node photomask specifications. This paper discusses the defect measurement by AIMS157. Evaluation using programmed defect mask, repeatability is analyzed changing the optical parameters. Static and dynamic measurements were evaluated and the result shows the improved accuracy. It shows the possibility to be applied on 65nm node and smaller feature size.
In modern mask manufacturing, a successful defect mitigation strategy has been become crucial to achieve defect free masks for high-end lithography. The basic steps of such a strategy include inspection, repair, and subsequent post-repair qualification of repair sites. For the latter task, actinic aerial image measurements have been proven to be the technique of choice to assess the printability of a repaired site. In the last three years, International SEMATECH in cooperation with Infineon/AMTC-Dresden and SELETE, funded a joint development project at Carl Zeiss to develop an AIMS tool operating at the 157nm wavelength. The three beta tools were shipped in 2003 to the three beta customer sites. In this paper are presented the first results obtained with these beta tools, including measurements on binary as well as alternating phase shift masks. The technical properties of the tool were discussed with regards to the capability of the tool for defect qualification on photomasks. Additionally, preliminary results of the evaluation of alternating phase shift masks will be discussed, including measurements performed on dense lines-and-spaces structures with various pitch sizes.
One of the key challenges for the successful implementation of EUV Lithography (EUVL) is the supply of defect free mask blanks. Obviously a reliable defect inspection is a prerequisite to achieve this goal. We report results from a EUVL blank inspection tool developed by Lasertec. The inspection principle of this tool is
based on confocal microscopy at 488nm inspection wavelength. On quartz substrates a sensitivity of 60nm is demonstrated. On buried defects in the multilayer stack a reasonable capture rate down to approximately 25nm defect height has been measured. We compare these results to previously reported data on the wafer version
(M350) of the current M1350.
The challenge to achieve an early introduction of 157 nm lithography requires various advanced metrology systems to evaluate the 65 nm node lithography performances, equipments and processes. Carl Zeiss AIMS tool based on the Aerial Image Measurement Software is the most promising approach to evaluate the mask quality in terms of aerial image properties, in order to assess post repair quality. Selete has joint activities with Carl Zeiss, International SEMATECH and Infineon to accelerate the development of an AIMS tool operating at the 157 nm wavelength. The alpha tool phase of the project has been completed, and beta tools are currently being built. This paper is discussing the results from measurements on the alpha tool of some 157 nm attenuated phase shift masks (Att-PSM). Resolution results and CD evaluation with respect to these measurements will be presented.
The first Aerial Image Measurement System (AIMSTM) for 157 nm lithography worldwide has been brought into operation successfully. Its performance will be demonstrated by AIMSTM measurements at 157 nm wavelength on binary chrome masks. Several through focus series have been measured in order to calculate the process windows for various structures with feature sizes at mask level of 300 nm and below. The latest results on enhanced illumination stability will be presented and a resolution that will enable an extension of the tool usage down to the 45 nm node. Using off-axis illumination 150 nm lines and spaces mask structures have been resolved.
The worldwide first Aerial Image Measurement System (AIMS) for 157 nm lithography has been used to measure binary chrome and attenuated phase shift masks at 157 nm wavelength. The AIMS measurements were done for line structures from 200 nm up to 400 nm and for 500 nm contacts. Through focus series have been conducted to calculate the process windows for various structures and feature sizes.
The high volume inspection equipment currently available to support development of EUV blanks is non-actinic. The same is anticipated for patterned EUV mask inspection. Once potential defects are identified and located by such non-actinic inspection techniques, it is essential to have instrumentation to perform detailed characterization, and if repairs are performed, re-evaluation. The ultimate metric for the acceptance or rejection of a mask due to a defect, is the wafer level impact. Thus, measuring the aerial image for the site under question is required. An EUV Aerial Image Microscope (“AIM”) similar to the current AIM tools for 248nm and 193nm exposure wavelength is the natural solution for this task. Due to the complicated manufacturing process of EUV blanks, AIM measurements might also be beneficial to accurately assessing the severity of a blank defect. This is an additional application for an EUV AIM as compared to today’s use.
In recognition of the critical role of an EUV AIM for the successful implementation of EUV blank and mask supply, International SEMATECH initiated this design study with the purpose to define the technical requirements for accurately simulating EUV scanner performance, demonstrating the feasibility to meet these requirements and to explore various technical approaches to building an EUV AIM tool.
This paper discusses the challenges to alternating phase shift mask defect inspection and new approaches for phase defect detection using multiple illumination methods in conjunction with defect detection algorithm modifications. Die-to-die inspection algorithms were developed for the KLA-Tencor 365UV-HR (APS algorithm) and TeraStar SLF27 (TeraPhase algorithm) inspection systems based upon the use of simultaneous transmitted and reflected light signals. The development of an AltPSM programmed test vehicle is described and defect sensitivity characterization results from programmed phase defect reticles are presented. A comparison of the two approaches used for the different inspection systems is discussed. A comparison of TeraPhase to transmitted light only results from a programmed phase defect test mask shows improved phase defect detection results.
Alternating phase shift masks (altPSM) are gaining importance as a reticle enhancement technique to meet the ITRS Litho Roadmap sub-130 nm node line widths. AltPSM fabrication usually involves etching of the quartz substrate in order to form the phase shift structures. Defects can arise during the quartz-etching step from imperfections in the resist image thereby causing various forms of phase shifting defects on the reticle. These reticle phase shift defects can result in printable defects on the wafer. In order to prevent wafer yield loss from occurring, it is necessary to detect and repair the reticle defects. A die-to-die inspection algorithm using simultaneous transmitted and reflected light signals was developed for the KLA-Tencor TeraStar SLF27 inspection system. The algorithm processes the transmitted and reflected light signals in parallel to detect both phase and chrome defects at high speed. One of the several challenges in the use of reflected light for pattern defect detection on alternating phase shift masks is to ignore lithographically insignificant mask process artifacts such as bright chrome 'halos' which may exhibit significant differences between adjacent die. This paper discusses the inspection challenges of alternating phase shift masks. Defect sensitivity characterization results from programmed phase defect reticles are presented.