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.
Direct phase-shift measurement is one of the key technologies to realize Phase-Shift-Mask (PSM) application. Most mask makers are developing practical PSMs for 157nm lithography. Final tuning of the optical parameters and quality assurance of them require accurate measurement tool of phase-shift and transmittance with 157nm light
illumination. In this paper, we will report the development of the system, which measures the phase-shift and transmittance of 157nm PSM at wavelength. This system has a 157nm F2 laser as a light source of the illumination and CaF2 optics with a CCD camera for the imaging. Key component is the interferometer, which has a function of lateral image shearing and phase modulation. The same technology is used in the current UV and DUV tools already exist. N2 purge and vacuum environments are newly introduced for the optical path to minimize attenuation of 157nm light by O2 and H2O. A fluctuation of the attenuation in the optical path significantly affects the short-term measurement repeatability. A new measurement algorithm, which uses two measurement spots on a PSM image, gives better repeatability than using single measurement spot under such unstable condition. Because most fluctuations are common elements to both of the two spots, they can be canceled out by the new calculation algorithms for phase-shift and transmittance measurements. The system with new techniques shows enough performance for the requirement of 157nm PSM measurements with new techniques.
Carl Zeiss is currently in the final phase of an AIMS 157 development program in cooperation with Selete, Infineon and International SEMATECH. Based on Carl Zeiss' proven AIMS (Aerial Image Measurement System) technology, the new tool can optically emulate the aerial image generated in any given 157 nm scanner. Beta tools will be shipped throughout 2003. In this work the AIMS fab 157 hardware concept will be described. Latest measurements show that
compared to first measurements CD repeatability and illumination uniformity could be significantly improved.
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 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.