Ulrich Dr. Strößner

Concept and feasibility of aerial imaging measurements on EUV masks

On the road to and beyond the 22nm half-pitch on chip patterning technology, 13.5nm EUVL is widely considered the best next technology generation following deep ultraviolet lithography. The availability of an actinic measurement system for the printability analysis of mask defects to ensure defect-free mask manufacturing and cost-effective high-volume EUV production is an infrastructural prerequisite for the EUVL roadmap and represents a significant step toward readiness for commercialization of EUV for high-volume-manufacturing . Carl Zeiss and SEMATECHs EUVL Mask Infrastructure (EMI) program started a concept study and feasibility plan for a tool that emulates the aerial image formed by a EUV lithography scanner supporting the 22 nm half-pitch node requirements with extendibility to the 16nm half-pitch node. The study is targeting a feasible concept for the AIMSTM EUV platform, bridging a significant gap for EUV mask metrology.

Development status and infrastructure progress update of aerial imaging measurements on EUV masks

The high volume device manufacturing infrastructure for the 22nm node and below based on EUVL technology requires defect-free EUV mask manufacturing as one of its foundations. The EUV Mask Infrastructure program (EMI) initiated by SEMATECH has identified an actinic measurement system for the printability analysis of EUV mask defects to ensure defect free mask manufacturing and cost-effective high-volume EUV production as an infrastructural prerequisite for the EUVL roadmap ([1], [2]). The Concept and Feasibility study for the AIMSTM EUV resulted in a feasible tool concept for 16nm defect printability review. The main development program for the AIMSTM EUV has been started at Carl Zeiss leading to a commercialized tool available in 2014. In this paper we will present the status of the progress of the design phase of this development and an infrastructure progress update of the EUV Mask defect printability review.

Wafer level CD metrology on photomasks using aerial imaging technology

Recently more and more mask designs for critical layers involve strong OPC which increases the complexity for standard CD SEM mask measurements and conclusive interpretation of results. For wafer printing the wafer level CD is the crucial measure if the mask can be successfully used in production. Recent developments in the AIMSTM software have enabled the user to use the tool for wafer level CD metrology under scanner conditions. The advantage of this methodology is that AIMSTM does see the CD with scanner eyes. All lithographic relevant effects like OPC imaging which can not be measured by other tools like mask CD SEM will be captured optically by the AIMSTM principle. Therefore, measuring the CD uniformity of the mask by using AIMSTM will lead to added value in mask metrology. With decreasing feature sizes the requirements for CD metrology do increase. In this feasibility study a new prototype algorithm for measuring the lithographically relevant AIMSTM CD with sub pixel accuracy has been tested. It will be demonstrated that by using this algorithm line edge and line width roughness can be measured accurately by an AIMSTM image. Furthermore, CD repeatability and tool matching results will be shown.

Programmed defects study on masks for 45nm immersion lithography using the novel AIMS 45-193i

Mask manufacturing for the 45nm node for hyper NA lithography requires tight defect and printability control at small features sizes. The AIMSTM1 technology is a well established methodology to analyze printability of mask defects, repairs and critical features by scanner emulation. With the step towards hyper NA imaging by immersion lithography the AIMSTM technology has been faced with new challenges like vector effects, polarized illumination and tighter specs for repeatability and tool stability. These requirements pushed the development of an entirely new AIMSTM generation. The AIMSTM 45-193i has been designed and developed by Carl Zeiss to address these challenges. A new mechanical platform with a thermal and environmental control unit enables high tool stability. Thus a new class of specification becomes available. The 193nm optical beam path together with an improved beam homogenizer is dedicated to emulate scanners up to 1.4 NA. New features like polarized illumination and vector effect emulation make the AIMSTM 45- 193i a powerful tool for defect disposition and scanner emulation for 45nm immersion lithography. In this paper results from one of the first production tools will be presented. Aerial images from phase shifting and binary masks with different immersion relevant settings will be discussed. Also, data from a long term repeatability study performed on masks with programmed defects will be shown. This study demonstrates the tools ability to perform defect disposition with high repeatability. It is found that the tool will fulfill the 45nm node requirements to perform mask qualification for production use.