Hidemi Kawai

Nikon EUVL development progress update

Extreme Ultra Violet Lithography (EUVL) has been widely regarded as the lithography technology to succeed optical lithography. It is now considered as one of the most promising technologies below hp45nm node [1], following ArF immersion lithography considering trend of achievable process K1 factors shown in Fig. 1. In this paper we would like to present significant progress on the development of EUV exposure tool. There are several key important areas which should be developed to realize EUVL to be feasible such as reflective mask, resist, and tool itself. The reflective mask features such characteristics as pellicle-less, ultra-smooth blank flatness and defect free. The resist should be of high sensitivity and small line edge roughness (LER) as well as fine resolution. EUV exposure tool itself consists of major modules such as EUV light source, projection optics, vacuum body, vacuum stages, and so on. As far as EUVL optics development is concerned, through the development of high-NA small-field EUV exposure system (HiNA) in conjunction with EUVA (Extreme Ultraviolet Lithography System Development Association) projects, we have developed new polishing technologies such as ion-beam figuring and elastic emission machining, and new ultra high-precision interferometers for aspheric surface metrology. Wave front sensor system has been also developed partly in EUVA project. A new wave front sensor system which can be used for evaluating the projection optics with EUV light has already been installed in New SUBARU synchrotron facility in University of Hyogo. Our multi-layer coating technology has been also improved. High reflective Mo/Si multi layer coating has been successfully achieved and irradiation tests using synchrotron radiation have been conducted [8]. Successful achievement of those developments enables us to produce full-field projection optics for EUVL process development tool called EUV1. Proto-type development of full-field projection optics has been successfully completed and evaluated to be of enough performance. Preparation of complete set of production and metrology tools necessary for projection optics production was completed and all tools are now in full operation. Nikon has studied reticle protection method and developed Dual Pod Concept in cooperation with Canon. Nikon also has developed its own reticle cover to be implemented in EUV1 tool. Nikon has completed almost all module fabrication such as full-field projection optics module, illumination optics module, vacuum body module, vacuum compatible reticle/wafer stage modules, reticle/wafer loader modules, and EUV light source module. Nikon has already got into module integration production process to meet EUV1 development schedule. Nikon announced to start EUV1 tool installation in 1st half of 2007 and has been proceeding it on schedule. Nikon also would like to announce that development of 1st generation production EUVL tool dubbed EUV2 is now considered and that system concept design is under way.

Current development status of HSFET (High NA Small Field Exposure Tool) in EIDEC

In EIDEC, a micro extreme UV (EUV) exposure tool for next-generation lithography has been developed, referred to as a High NA Small Field Exposure Tool (HSFET), and its basic configuration is as follows: Xe DPP source, critical illumination configuration, a rotationally moving turret with several sigma apertures, a larger than 30 × 200 μm field size, and variable NA mechanics to cover from 0.3 to 0.5 NA and beyond. The PO optical performance is well suited to our required 11 nm half-pitch patterning. The transmitted optical wavefront error (WFE) was measured and confirmed to be 0.29 nm RMS, which is far less than the required value of 0.6 nm RMS, and the tool was successfully installed in August 2015. Here we show the exposure results using a newly designed reticle for HSFET patterning. We report the basic printing performance and consideration for high-NA effects as know n polarization effects.

Development of EUV lithography tools at Nikon

Full-field EUV exposure tool named EUV1 integrated and exposure experiments were started with the numerical aperture of the projection optics of 0.25 and conventional partial illumination with coherence factor of 0.8. 32nm elbow patterns were resolved in full arc field in static exposure. In the central area 25nm line-and-space patterns were resolved. In scanning exposure, 32nm line-and-space patterns were successfully exposed on a full wafer. Wavefront error of the projection optics was improved to 0.4nmRMS. Flare impact on imaging was clarified depend on the flare evaluation using Kirk test. Metal oxide capping layer and oxygen injection method were developed for the contamination control in EUV exposure tools. High-NA projection optics design is also reviewed.

Total overlay analysis for designing future aligner

We found total overlay with respect to optical lithography using an approach similar to quality control technique employed at a semiconductor factory. This approach involves an aligner performance, process quality, reticle error and overlay measurement. This paper further describes new ides for the number of machines to be used for matching and data collection period. Lastly, improvement on total overlay and a prospective view for a future aligner and its usage are also described.