Peter Kuschnerus

Electron-beam-based photomask repair

High-resolution electron-beam-assisted deposition and etching is an enabling technology for current and future generation photomask repair. NaWoTec in collaboration with Carl Zeiss NTS (formerly LEO Electron Microscopy) has developed a mask repair tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, extreme ultraviolet masks, and e-beam projection stencil masks. Specifications currently meet the 65nm device node requirements, and tool performance is extendible to 45nm and below. The tool combines LEO’s ultra-high-resolution Supra scanning electron microscope platform with NaWoTec’s proprietary e-beam deposition and etching technology, gas delivery system, and mask repair software. In this article, we focus on tool performance results; that is, the reproducibility and accuracy of repair of clear and opaque programmed defects on Cr binary and MoSi phase shift masks. These masks have in the past been difficult to repair due to beam position instability caus...

Application data of the electron beam based photomask repair tool MeRiT MG

With the ever decreasing feature sizes and increasing cost of current and future photolithographic masks the repair of these masks becomes a substantial factor of the total mask production cost. In collaboration NaWoTec GmbH, Carl Zeiss Nano Technology Systems Division and Carl Zeiss Semiconductor Metrology Systems Division have launched a mask repair tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, EUV masks, and e-beam projection stencil masks. In this paper, besides a brief overview of the tool platform, we will present the automated repair of clear and opaque defects on Cr and MoSi quartz masks. Emphasis will be put onto the resolution and the speed of the repair procedure and the high grade of automation and integration achievable in the repair of highend photomasks. An outlook against the ITRS requirements and the extendibility of the presented solution to further technology nodes will be given in the summary.

Actinic aerial image measurement tool for 157-nm mask qualification

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.

Aerial Image Measurement System for 157 nm Lithography

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.

Actinic aerial image measurement for qualification of defect on 157-nm photomask

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.

Microscope Illumination Systems for 157 nm

The image quality of an inspection microscope depends strongly on the performance of the illumination system. Especially in the case of laser-based illumination it is necessary to transform the original beam profile into a homogeneous light spot with a flat top field distribution. Simultaneously, speckles caused by the coherence of the laser have to be reduced. Here we discuss different ways to homogenize the multi mode beam profile of a pulsed compact 157 nm excimer laser. A variety of setups, combining dynamic acting diffusers, microlens arrays and primary lenses were realized and characterized in several geometrical arrangements. The homogenizers were evaluated and characterized especially with respect to the statistical behavior on the integrated pulse number.

Performance of the aerial image measurement system for 157-nm lithography

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.